There are no mods that will provide significant gains for a reasonable amount of money with the 7M-GE. Actually I have a few friends who've spent obscene amounts and have nothing to show for it that a stock GTE can't beat the crap out of with $300 in parts.... They've spent thousands (A couple are mechanics and one's a machinist, they're not paying any of that for labor).
Do as you like, naturally. There's a lot of good info on this site and I hope you'll find it of use; There's also some bad info here and there, if in doubt, ask.