Well, if it was me, I would only want it done if not doing so was going to have a substantial/noticeable effect on my health. Has the orthodontist explained why you need it/what will happen if you don't get it? Go and talk to them, it's surgery after all, it is a 'big deal', find out the details so you can make an informed decision.
At the same time, I would discourage you from avoiding it if you need it just because it seems scary.