I'm cheap and fixed the front fan on my 84 with just cleaning and lube.
The fan motor bearings were so dry/stiff enough that the fan would not
start on low, I had to start it on medium or high, then switch to low.
After the lengthy prrocess of removing the dash and splitting the
heater plastic housing, I removed the motor, disambled it and soaked
the felt at the bearings with Gumout and blew dry with air. I repeated
this a few times to clean out the crud and then oiled the bearing and
felt with "turbine oil" from an appliance parts shop, comes in bottle
with a "zoom" pull out spout, it's a great long lasting oil for bushing
type bearings. Reassembled the heater with sealant made from thin
strings of "mor-tite" rope caulk. I's been years and no problems or
squeaks. While I was in there I also replaced the foam on the flaps
that act as gaskets. I did the same thing to my Jetta, and unfortunately
the fan now clicks slightly, so this repair might not always be fool proof
but i did save a couple of Benjamins.