Baron issues

Well, in three days of flying a long cross country to West Texas from
Wisconsin, my autopilot went nuts in the roll axis- wouldn't capture flight
director or heading bug info, and just tried to do uncommanded turns.
Altitude and pitch worked fine.

Suspected a bad roll servo- could be driver transistors or even a motor. Was
told a new motor (if available) could be up to $3000. Had to hand fly back
from Texas in IMC- not much fun and pretty tiring.

Pulled the back cover off and yes, it sure looks like a servo- but no way to
tell if it works until it gets into the avionics shop.

Any help on testing the unit while still installed? There is resistance to
aileron input with the autopilot on, but the servo won't turn or capture
heading bug or FD input.

Then, in a routine post flight, I tried the strobes- no luck. The tail flash
tube looks a little blackened- does anyone know if the wing tip units will
continue to work if the tail tube is dead?

Or, does this sound like a power supply issue?

All of this is getting to sound expensive as well as being a pain- any
advice or commiseration would be appreciated. BTW the plane is a B-55 Baron.

TIA