[Nicodemus]

I actually went to Watcher's Keep before I went to Spellhold, and I made it through alright. Some of it is a little hairy, but by design, it's going to be tough no matter what level you are.

Keep in mind too, that you get insane amounts of experience points, so you are bound to go up at least a few levels in the process. My thief went up 5 or 6 levels. And if all else fails, you can do as the others have said and take a break from it if it gets too gnarly. I highly recommend going, even if it's just to cruise through the first floor. It's relatively easy, and there's some very nice loot.