Gemcitabine Hydrochloride With or Without Vismodegib in Treating Patients With Recurrent or Metastatic Pancreatic Cancer

Inclusion Criteria:

* Patients must have histologically or cytologically confirmed adenocarcinoma of the pancreas
* Patients must have measurable disease, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded) as \>= 20 mm with conventional techniques or as \>= 10 mm with spiral computed tomography (CT) scan
* Patients must have either:

  * Newly diagnosed chemo-naïve metastatic pancreatic cancer; only patients who have not received any chemotherapy for their metastatic disease are eligible
  * Recurrent disease after curative-intent surgery which has now recurred and is metastatic; patients who have recurrent disease may have received adjuvant chemotherapy or adjuvant chemoradiation, but may not have received any chemotherapy for metastatic disease; adjuvant therapy must have been completed \>= 6 months prior to the diagnosis of recurrent disease, or if not adjuvant therapy received, surgery must have been performed \>= 6 months prior to the diagnosis of recurrent disease
* Age \>= 21 years
* Life expectancy \> 3 months
* Karnofsky performance status \>= 80%
* Granulocytes \>= 1,500/mcL
* Platelet count \>= 100,000/mcL
* Total bilirubin =\< 1.5 times upper limit of normal (ULN)
* Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) =\< 2.5 times upper limit of normal (ULN) (=\< 5 times ULN in the presence of liver metastases)
* Creatinine within normal institutional limit (\< 1.5) OR creatinine clearance \>= 65 mL/min/1.73 m\^2 for patients with creatinine levels above institutional normal
* International normalized ratio (INR) =\< 1.5 (=\< 3 for patients on warfarin)
* Patients who are on warfarin anticoagulation are allowed to participate as long as they fit the following 4 criteria:

  * They are therapeutic on a stable warfarin dose
  * Their INR target range is no greater than 3
  * They are monitored with weekly INR testing
  * They have no active bleeding or pathological condition that carries high risk of bleeding Other anticoagulants, including enoxaparin (Lovenox) and fondaparinux (Arixtra) are also permitted
* Women of child-bearing potential and men must use at least one form of contraception (i.e., barrier contraception) at least 4 weeks prior to study entry and then two forms of contraception (i.e barrier contraception and one other method of contraception), for the duration of study participation, and for at least 12 months post-treatment; for appropriate methods of contraception considered acceptable; should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately
* Pregnancy Testing: Women of childbearing potential are required to have a negative serum pregnancy test (with a sensitivity of at least 25 mIU/mL) within 10-14 days (at initial screening/consideration for the trial - serum or urine); a pregnancy test (serum or urine) will be administered every 4 weeks if their menstrual cycles are regular or every 2 weeks if their cycles are irregular while on study within the 24-hour period prior to the administration of GDC-0449; a positive urine test must be confirmed by a serum pregnancy test; prior to dispensing GDC-0449, the investigator must confirm and document the patient's use of two contraceptive methods, dates of negative pregnancy test, and confirm the patient's understanding of the teratogenic potential of GDC-0449
* Ability to understand and the willingness to sign a written informed consent document
* Patients with recurrent disease after curative-intent surgical resection must have sufficient archival material for correlative studies (20 unstained 5 micron slides and 20 unstained 10 micron slides, or an archival tissue block

Exclusion Criteria:

* No prior chemotherapy for metastatic pancreatic cancer; patients who have received any chemotherapy and/or radiation therapy in the adjuvant setting must have completed this therapy ≥6 months prior to enrollment on the trial at the time of recurrence
* Patients may not be receiving (or received prior to enrollment) any other investigational agents for metastatic disease
* Patients with known brain metastases should be excluded from this clinical trial because of their poor prognosis and because they often develop progressive neurologic dysfunction that would confound the evaluation of neurologic and other adverse events
* History of allergic reactions attributed to compounds of similar chemical or biologic composition to hedgehog antagonist GDC-0449 or any other agents used in this study
* History of allergic reactions attributed to compounds of similar chemical or biologic composition to GDC-0449 or other agents used in the study
* GDC-0449 inhibits CYP2C8, CYP2C9, and CYP2C19 drug metabolism enzymes in vitro at concentrations that may be clinically relevant. Therefore, caution should be exercised when dosing GDC-0449 concurrently with medications that are substrates of CYP2C8, CYP2C9, and CYP2C19 and have narrow therapeutic windows
* Patients with malabsorption syndrome or other condition that would interfere with intestinal absorption; patients must be able to swallow capsules
* Patients with clinically active liver disease, including active viral or other hepatitis or cirrhosis are ineligible
* Patients with uncontrolled hypocalcemia, hypomagnesemia, hyponatremia, or hypokalemia, defined as less than the lower limit of normal for the institution, despite adequate electrolyte supplementation are excluded from this study
* No currently active second malignancy other than non-melanoma skin cancer or carcinoma in-situ of the cervix; patients are not considered to have a "currently active" malignancy if they have completed therapy and have no evidence of recurrence for at least 5 years
* Uncontrolled intercurrent illness including, but not limited to,

  * Ongoing or active infection,
  * Symptomatic congestive heart failure
  * Unstable angina pectoris
  * Cardiac arrhythmia
  * Psychiatric illness or social situation that would limit compliance with study requirements
* Pregnant women are excluded from this study; breastfeeding should be discontinued if the mother is treated with GDC-0449; these potential risks may also apply to other agents used in this study
* Human immunodeficiency virus (HIV)-positive patients on combination antiretroviral therapy are ineligible because of the potential for pharmacokinetic interactions with GDC-0449; in addition, these patients are at increased risk of lethal infections when treated with marrow-suppressive therapy; appropriate studies will be undertaken in patients receiving combination antiretroviral therapy when indicated