E -
The RMS issue in these cars have been extensively beat to death, yes there were some problem cars but as posted earlier there have been revisions to the seals done at the factory as well as some dealerships, however most of the dealerships installed new motors on the cars that were under warranty when the problem came up.
If you are looking to purchase a used 996 buy one that has been regularly driven with mileage over 30K and you should be ok as the failure routinely showes itself prior to this, if you are looking at a car with the miles on it then you should be fine.
Todd
Ps... If you do a search (996 RMS) you will get more hit's than you care to read.