Did he change the capacitor as well?
No. Just the board and motor.
It's a DC motor - with 2 "wiring harnesses" running to it. One with a few wires, and the other with a bunch of them. Would the capacitor be on the motor, or somewhere in the furnace?
no, none there as it is varibale speed motor.
Did they replace the end bell only, the motor only or the entire end bell/motor assembly?
Just the motor.
It is common that the end bell electronics are usually is what goes out
There is available a test meter to take the guess work out of this
I think it is called ICM 2 tester
But since the motor has been replaced, I am sure it is the end bell.
This is getting really expensive for you, first a motor, then a circuit board. While there are generic circuit boards, I can almost assure you Lennox had a replacement board for your unit. I would be suprised if they don't. They do however change boards fairly often and at times you may need a conversion kit.
If I can be of further assistance please let me know.