Liz, i've always said that you have been one of the most successful examples of good "banding" that i've met. To get a band to work so well takes lots of willpower and motivation. Therefore , if you can do that well with a band, imagine what you can do with a bypass !!
This waiting period is a breeding ground for feelings of uncertainty and fear, but this will pass in time and you will soon adjust to the transition.
Yes it will be slightly different due to the sugar intolerence you may experience, but the restrictive elements are similar, so you have a head start on most people as you've experienced those things before.
It's a shame that the only reason you are in this position is because of "technical" problems, but everything happens for a reason. This way, as people have pointed out, there'll be instant results post op as you don't have to wait for a fill and no frequent hospital visits for refills. Plus, this time its for keeps - no worries about future technical problems and subsequent weight regains (yes, i know you can gain with a bypass but it wasn't an issue for you when your bands were working so i can't see it would be with a bypass !!)
From a selfish perspective, you'll be doubly useful to the rest of us as you will have even more experience than before !
You have a wonderfully supportive family around you and lots of friends to lean on along the way - you'll be fine x x