Blower fan inoperative - and buzzing?

Ladies and Gents:

(Problem is with a 1989 300E)

I recently refilled my cooling system after replacing a freeze plug. Afterwards, I turned the Climate Control to full warm to circulate the new cooolant through the heater core. I switched the blower from low to "AUTO", then eventually to the "high" setting. Shortly thereafter, the blower motor stopped.

I have noticed that now, while the car is running, I hear what sounds like a buzzing sound coming from the area of the blower motor.

Is it possible that the fan motor is jammed, but still receiving power? I checked Fuse 7, which I believe is related to the blower motor, and it looked fine.

I am planning to access the motor tommorrow and have a look at it. The problem is, I have never doneany major electrical troubleshooting and I don't know where to start on this problem. I have the 124 service CD, although trying to find the right circuit diagram is a pain in the *** with the way the CD is laid out.

Could the problem be related to the ACC blower switch, or is it possible that the blower motor actually is jammed or seized? Any wisdom or suggestions?

Any help would be appreciated before I throw in the towel and take it to a shop.