My 92 Honda Accord heater fan motor did not work all of a sudden one morning when I started my car with my car starter. What could the problem be? (fuse,motor) and how difficult is it to fix?

Definitely check you manual to see which fuses handle the fan motor, could be a relay too. Check all of them and replace if necessary. If all else fails you'll need to check the fan motor itself. I have run temporay feed wires from the battery to the motor. I put in an in-line 25 amp fuse for saefty. I applied to two wires directly to the fan motor terminals. In my situation the fuse blew instantly because the fan motor was shot. Replacement varies so much from vehicle to vehicle I can't begin to start. Iwas a huge job in my case starting with removing the right front wheel and fender. YUK

Most likely a fuse or relay problem. Use one of the methodologies for testing fuses, explained in the link below, to test all under-hood and under-dash fuses:

https://www.askmehelpdesk.com/cars-t...tml#post252145

The under-hood fuse and relay box also contains a heater relay that you want to check out.