I've had the compressor magnetic clutch/pulley bearing needing replacement on a 96 E50 and 01 CLK320. Both were compressor-out to do the job.

Servicing the pulley/clutch/bearing was straightforward. It was basic hand tools and a 3-jaw puller IIRC, but would be difficult in situ because of space.

Did not need to do shaft seals in both cases.