I put a used tranny in and it's having some issues. Grinds going into 5th gear, doesn't want to downshift back into 2nd or 1st.

My old tranny was fine, atleast the gears were and Im pretty sure the differential... but the housing was all busted up. What I'm wondering is how hard it is to swap the gears out from one to another. Would it be too much for a mildly experienced person, or should I take it to a mechanic? Im trying to save myself from buying a new transmission.

That's definately not a novice task (I'm not sure what you consider yourself mechanically). They shouldn't charge much at a shop if you were to take them in.

BTW, the bellhousing is the big flared out peice on the tranny that covers the clutch, etc... and bolts the tranny to the block.