The main purpose of this study is to learn whether or not the combination of gemcitabine, bevacizumab and erlotinib works in treating patients with advanced or metastatic pancreatic cancer. Bevacizumab is a new anti-cancer drug. It is an antibody that works to slow or stop cell growth in cancerous tumors by decreasing the blood supply to the tumors. It is approved by the FDA for the treatment of colorectal cancer but is still considered investigational for treating pancreatic cancer.