Depends on the part and depends on the indy.

I realize that the indies make part of their living on the parts makup. They have kids in school and taxes to pay just like everybody else. So I usually don't even try with relatively cheap parts like timing belts and oil filters, and (obviously) I won't if it's an emegency repair. I'll also buy my own Mobil-1 because most shops can't get it any cheaper than I can.

Generally speaking, my break-even level of involvement is usually at about $100 parts.

Sometimes I buy the part at full price from the Volvo dealer and bring it to the shop doing the work, eg. I'm finally getting my rear iPd bar replaced, I'm also replacing my struts and shocks with Bilsteins and replacing the spring seats. Now, I'm using parts from 3 different sources, and I want the correct hardware used, there are a bunch of unique parts like one-way nuts in the Volvo suspension. Had I left all this to the shop doing the work, it either wouldn't get done correctly, or they'd be on the phone for 2 hours tracking down the parts, which they'd charge me for. It seems to work better if I do the actual legwork for repairs like that.

-Punxsutawney Phil