If you've installed Oblivion and mods (etc.) in the default location, I suggest doing a clean uninstall and a fresh install, but this time, installing outside of Program Files (or the x86 version, in your case) - I use C:\Games\Bethesda Softworks\Oblivion for example, but there are plenty of other directory names you could use.
Also, you might want to check out http://tesivpositive.animolious.com/. There is a ton of vital information there. In addition, check the current thread (look in the first, say, 10 pages of threads at least) for each mod you're interested in. And if you have questions about that specific mod, ask there.
Wrye Bash can take a bit of getting used to, but it is well worth it, once you understand the basics. And from there, it only gets better (e.g., BAIN installations...)
edit: Oh, and one thing you'll probably hear again and again, but which is
absolutely essential, is that you *must* do something about Archive Invalidation - most likely, this will mean telling either Wrye Bash or OBMM to get Oblivion to use BSA Redirection.