1990 Lexus LS 400 Heater fan screeches/rumbles

Heater problem
1990 Lexus LS 400 V8 Two Wheel Drive Automatic

I think my heater fan bearing may be out. Do you know how difficult this is to replace - that is, can I do it myself?
How difficult is it to get to?

I'm fairly mechancially inclined and do the more simple mechanical repairs on my cars like brake calipers, water pumps, window linkages.

I was told by a relative that fixiing the heater fan (bearing) is fairly easy. But I'm unsure and wanted to ask you before I started this myself.