My Doctor told me that having the surgery is not only a life but lifestyle changing experience that will test every bit of will and determination you have. That is the scariest part. The surgery is nothing.
Yes there are risks, but they are minimal. Very minimal compared to how long you may live if you continue on as you are now.
As far as the risk of your stomach leaking after surgery, the odds of that happening are very very small. Your Doctor will staple, clamp, and glue you. And the morning after surgery they will take an Xray to make sure nothing is leaking.