Engine/Tranny upgrade help needed

Since my 99 8G is fastly approaching 200K(should hit it that mark by 8/2004), I plan to go ahead and get another V6 engine and tranny to replace the stock ones. But before my current ones go out, I need some advice on how to "beef up" the extra ones I find. I plan on getting the spare tranny "bullet-proofed", but what else should I do to it? And as for the engine, should anything be done to the internals while it is just sitting, to get more HP from it? I'll probably get SDS once the second engine goes in too. Also since I don't know too much about engine upgrading, since I mostly deal with visual mods rather that performance, if you could point me to some engine upgrading websites or books that would help out alot. Afterall, I'd hate to just take it to a engine rebuild shop and say "Put some more horses in here, please.", without knowing what they will do. i like to know what I'm talking about when I get something done.