There are actually several kinds of ETS surgery...
All of them do the same thing though, cutting the nerve...What is most important to figure out is at what spot they cut the nerve (T3, T4, T2?) I don't know the specifics of it since I'm not going to do ETS for the forseeable future (if at some point I'm convinced it can be done relatively safely with the least as possible side effects and no other treatments will be available, it might be an option at some point...) but if you are, that is the most important thing to figure out.
Also...What has worked for some people is just cut the nerve on one side (for instance, the right side, because you do most things with the right hand). That way the compensatory sweating and everything can be a little reduced because some part of your upper body can still sweat...
Just do some research on google...hyperhidrosis + ETS, disgard the commercial sites (mostly a bunch of assholes trying to make money on other peoples' misery) and read some scientific studies about it. Oftentimes you'll be able to read abstracts of studies and if you happen to be a student you can access things like wiley science and other sites like that...It's a one time deal so you want to make sure you do it the way you want, and not just go to the first doc out there and let him cut something up.