I am a Type 1.5 (more like a Type 1) and had RNY in September. My surgeon ABSOLUTELY did not require me to do that crazy pre-op diet because of my dietary needs. He told me not to change anything actually, because keeping my blood sugars stable prior to surgery took precedence over everything! I would encourage you to talk to them today and ask not to have to do that. All I had to do was fast after midnight prior to surgery.
As to managing after surgery, please work closely with an endocrinologist - either your own or smoeone in the hospital. I had both. I didn't need any insulin at all for the first 2 days after sugery, but as soon as I started on anything with calories, I did need insulin. We started small and worked up because it's better to run a little high than to run too low in the early days.
Now, it only takes about 15 grams of carbs to treat a low. In the early days, I used milk or a small amount of juice. Now I do that, a glucose tab or a small Peppermint Pattie and that does it. I need fewer calories/carbs to raise my blood sugar.
Call your surgeon's office today and ask them to work with you. Mine was happy to do it when I asked - no problem. And I had mine done at the University of Penn in Philly - quite a well known leader in medicine on the East Coast.
Good luck and keep us posted!