i just bought a 98 gsr off a friend. hes done nothing to it but under the
hood almost everything seems to have a bit of corrosion and looks sh*tty
wondering what best ways to clean it up are, or good sites for replacement
parts. i'd like to have it looking nice enough to pop the hood without
cringing.

use Rust-Corrosion Removers, it works well for me.

any specific brand?

try check this out:
http://www.jmsonline.net/METAL-CLEAN...LISH---RUST-CO RROSION-REMOVERS.htm