I remember my 01,they are notorious for clips and or window regulator going bad.If the other regulators have not been replaced yet ,they will fail ,mine all did after the warranty ended.$500 plus each at dealer for RR.
in comparison , my 05 just had 1 front passenger regulator fail all its life_however ,both front door handle carrier has been replaced twice.(Febi belstein from FCP)-this is another thing to watch out for ...
just buy the regulator unit with with motor (inexpensive nowadays-aftermarket)but save the motor from the old unit if its still good you might need it one day.
Get dirty -welcome to the M54 family.