Along with the good points that Ron makes, I'll add that the shop I go
to often simply is unable to source the parts in a timely fashion from
his normal suppliers (including dealers). I once had one of my vans on
his lot for 3 months while he (and I) waited to get the front hub for
a syncro. After 3 months, I I finally ordered it from one of our
online vendors and had him install it.

Our online vendors do a good job in keeping us supplied with parts for
our aging (but precious) vehicles. The normal parts supply houses (and
dealers) don't.