AFAIK, there is no porsche-sourced IMS replacement. therefore, no 2-yr/unlimited mileage IMS part that can be swapped out when you get the RMS done.
however the RMS is replaceable. mine was done in dec '08 (prior to my purchase) and it's still not leaking -- *knock on wood!*
but you can get it done at another porsche mechanic (if they know how to do it) and get the clutch done/checked while you're in there.
since it all has to come out to do the RMS, the labor should be negligible for the rest.