Topsites, I use to demand old parts from shop, then it occurred to me that they could be giving me just any old part--maybe from their scrap pile. If a shop is dishonest, there's lots of ways to be dishonest.
Best way is to learn to do most of the work yourself--and I know you do topsites--I'm just talking in general here. Take it in if it's still in warranty--do it yourself if not!!! It doesn't take but a couple of succeses to get you hooked, and to put you ahead dollar wise--and yes, you will have a few goofs along the way!!!