A few posts down ooXxXoo has posted that he does mods, and he also does repairs on lots of systems (he also happens to be the Technical and Resto Forum moderator). His prices always seemed reasonable to me, but I never have used his services or price shopped that kind of thing.

I also believe InsaneDavid (sp?) mods and sells Genny's, so you might be able to save a bit just buying a modded one from him to save shipping one-way.