alternator?

hi folks, i hate asking questions i should know the answer to!! but here goes, i have a 85' gti cabby, my alternator bearings are noisy as hell!, my question is, what do i need to know before i buy one!? what amperage is it? are there different types? will a mk2 one fit? and best place to get one? oh! and new or reconditioned? cheer's for any replies,  :dontknow:  al.

Me i would walk in to any good motor shop and hand over the old unit pay and walk out with the new unit .

Job done .