The motor is replacable with a Honda scooter starter motor, many threads on that.
Unit can be flushed and refilled and seals replaced, several threads on that as well.
The pump, as far as I recall, is not a part one can buy alone on the aftermarket as BMW controls the distribution of this part and restricts it to its own use for sale in complete actuator assemblies only.
If you are looking for a working, used actuator assembly, they periodically appear for sale on this site.
I am sure others more versed than I will soon chime in with additional information.
They are fairly easy to work on - look in the "Files" "Technical" section for guidance. Most important thing is after you overhaul put in no more that 150 ml of oil or you will crack the case. I have found 135 ml to be optimal. There are several sources for the shaft wiper and shaft seal (only things that wear out and leak). The motor is an HS-50N scooter starter found at EMS Global for about $38. And a few members here offer rebuild services.
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