Any suggestions on how to troubleshoot the following problem

Flying club 182RG. Alternator CB trips intermittently and in most cases can be reset, but not always. Generally after reset it will continue working for several hours before tripping again.

Mechanic has looked at system without seeing an obvious fault. He theorized that a leaking crankshaft seal (since replaced, no change in alternator behavior) was causing it to overheat from blowby oil.

Any better diagnostic testing to do? If not, in what sequence should we start replacing parts. There have been suggestions to replace the voltage regulator.

Is it soaked in oil ?

Mineral oil is an insulator, thats why we fill line transformers with it. It could cause the belt to slip, but that would give you a low output warning, not a tripped CB. CBs age, consider replacing it. Also, in a cessna if one reset doesn't cure the problem, dont reset a second time.

A 182RG on our field had a breaker trip a couple of times, the technician (as I recall) just replaced the circuit breaker. A few flights later, there was a pretty good electrical fire, suspicion is chafing in main wire bundle behind firewall, upper left.

I think I'd spend some quality time cutting tie wraps and checking wiring.

There is a bulletin on certain alternator breakers that just keep tripping. The exact match replacement is unavailable and you have to use something else. There is a ceesna service bulletin on it.

I would, look behind the panel to verify the wiring to the cB isn't loose or touching ground. I would check the CB. I would have the alt checked, I would check the voltage regulator. If everything is fine, trace the wiring until you find one with worn insulation. Usually these are wires that pass thru the firewall, are zipped tied to an airframe part or control cable. Look for a loose group of wires. Vibration would cause them to touch intermittently.

...Also up along the pilot side doorpost where the aileron cable is routed with wiring for the strobe, LH position light, peto heat, flap, under-wing courtesy light, and cabin overhead lights/ map light.

One of the Cherokees I rent was doing something similar (twice to me on one flight) and it turned out to be a voltage regulator malfunction. Don't recall any CB's popping, just the entire panel going dark, turning master off and back on fixed it.