I had my thyroid removed because of a single cancerous nodule (which they didn't know for sure if it was cancer until they took it out), so I know how difficult making this decision is.
Unfortunately, your thyroid is all hormone function, basically. If you only had nodules on one side, you might be able to keep the other, but since it is on both, your doctor will defiantly want to take both.
There are a lot of possible side-effects of having your thyroid removed, too many to list here. Luckily, thyroid replacement hormones work really well and when you get the right dosage for you, you won't really know the difference.
I cannot stress enough how important it is to do your research. Educate yourself about your problem, the surgery, and possible complications. Ask your doctor any question you can think of and make sure he or she answers them to your satisfaction. Even get a second opinion if you still have reservations.
If you have any other questions, please feel free to post again.
Good luck and let us know how it goes.