My local Napa store has most of what I need and can get stuff next day in most cases if it's special order. And they're not morons either.

It helps that I know what I want, and since I sell parts, I also know how to find them or who to ask. If I need something that's strictly MB then I have a WD in Toronto for that. When a parts guy talks to another parts guy a lot of the usual crap is reduced.

Stuff like:
'' Well..... it's kinda round and it's about 4 inches long and it sits on the engine somewhere. NO...... wait..... it goes at the back, I think....... not sure, but I'm sure you'd have one. ''
'' Back of the engine or back of the car? ''
'' Ummm..... not sure, maybe back of the car? ''

'' Yeah, ( buddy ) I have those in stock. How many you need? ''

" Oh... Cool! Uh..... how much is it? ''
" $12.95 ''
'' Oh...... well, I was just wonderin' 'cause I have a used one, and now I know how much to ask for it. But thanks anyway, thanks for your time. '' ( at least he's polite )
'' Sure, don't mention it.'' ( really, don't )