Assuming it's the same or very similar to the mono wiper used on the 124, it takes more time to remove the plastic surround, than to disassemble the wiper assembly. It's an easy DIY job with no special tools needed.

If the steel shaft hasn't stripped the white plastic trans gear; clean out the old lube and use the same lube used for the sunroof. Reassemble & install without all the plastic surround. If it still doesn't work well, the motor is ng. Motor isn't rebuild-able. Buy used one for about $75 thru used-parts.com

Bob
PS Do search on mono wiper for instructions & photos and sunroof lube [about $5 for small container]