Take care to check the usual problems with cars from colder climates, like rust intrusion. Much of the Model S is aluminum, so you won't see much on the bodywork, but the suspension parts should be examined.
Drive units could go either way, IMO. The ones that have been replaced, save a few exceptions, are usually good. The ones that haven't been replaced still seem to start getting noisy. So you've got the choice between a vehicle where you know it was bad in the past, but is probably OK now, vs one that is an unknown. I think you'd have a hard time taking one side or the other, IMO.
But that point may be moot. Tesla may or may not provide you with vehicle histories. A few people have gotten them, but mostly Tesla says they won't provide the vehicle's history.
A couple common issues: drivetrain noises, sunroof problems, bent/damaged wheels, creased or dented frunks, and door handle trouble. From there the problems get more diverse. Inspect thoroughly before delivery.