Don't need to replace the motor just lubricate it. On the 124 chassis it is located under the windhshield-wiper motor (it has to come out to access the blower). Do a search on the subject , there is good info about it. Use ATF oil, it works. I did it 3 times already on my 124s. It takes about 1-2 hours depending on your skill level and urgency.
Good luck.

Alex