anyone do PCB repair?

I'm in the appliance trade and printed circuit boards are the norm now. Yet they are so expensive for the customer. I do get a mark-up on them, but I hate hate charging for a $300 board when a relay is all that is wrong.

So I have been teaching myself basic PCB repair.
I was wondering if anyone had suggestions for resources and specialty tools. (I have four different soldering irons and one gun, two of the irons are adjustable)
I can solder well but I don't have things like heatsinks or on board relay testers.

Generally when a board is bad it is 80% of the time a relay 15% a capacitor and 4% the contact pad and 1% other.
What spurred me to really start getting into this, is I had a customer friday. She is in a nice house, nice fridge, i didn't flinch when I gave her the $400 estimate. ($65 less than Bluebook) She brok out in tears. Mother dying of cancer, husband had recently died in a military accident. I felt so bad. I sat there working on her kitchen counter, testing the relays until I found a bad one. Went to my van, grabbed a hold board: I hold all exchanged control boards for 30 days, in case a customer has an issue requiring me to return their money and the new board for credit, then I have to give old board (there is a core charge of $60 on each one). I took a matching relay off the hold board, swapped it with her bad relay and voila her board worked. I charged her pure labor and saved her hundreds.

I actually make more this way and I wouldn't mind trying to be the local guy that does this service. As I like most other companies send boards off to Illinois or California for repair if i can't buy new. (most boards for machines made before 2003 can't be found)

So again. looking for a point to resources, guides, online classes. I feel strong I can do it now, but I like extended personal training because you learn better from multiple people in similar fields.