should i cop this for 30 or wait for the goty edition?
I'd say it's worth the thirty now, as GOTY can take a while to come out. But that's me, a big Fallout fan, saying this. If you like the series, but it's not a big deal to you, then wait. If you REALLY liked Fallout 3, go ahead and get it.
Answer To your spoiler, which I guess would also be a spoiler:
The ending is like Fallout 1 and 2, in that it tells you how you effected everyone, and after that, you can't play anymore. It makes sense, after you finish, because things change so drastically after that point. But, it does give you a big wall of text that you have to actually click a button, and would have to be retarded to miss it, tells you that you are about to go passed a point of no return, and gives you a choice to continue, or to wait, so you can make a save before you do that.