DO NOT get anything other than factory for this carrier. Aftermarket but high-quality bearings are OK to use (per what samiam44 says) but just get the factory parts through parts.com
Coincidentally I'm getting ready to do this exact job on my 560SEC this coming weekend. You have to drop the exhaust system (don't have to remove it totally from the car) to get enough room to gain access. Also you have to be VERY careful so as to mark things at the driveshaft to ensure correct alignment and balance upon re-assembly.
Doing the center support bearing is also an excellent time to do the flex disc(s) if they show any signs of wear, or you don't know that they've been done in the past 5+ years or more than 50K miles. Again, it's HIGHLY ADVISABLE to go with the factory part on the flex discs, and NOT to go with URO, Meyle or other brand flex discs.
Generally with the center support bearing, you'll hear (and sometimes feel) a loud clunk or clicking noise when you get on or let off on the throttle. That's generally the way you can tell that it's bad. Quite often it is the actual rubber carrier itself that is bad, not the bearing, but I recommend that the bearing AND carrier be replaced at the same time -- don't re-use the bearing as new ones are cheap.
A new drive-shaft center-support bearing/carrier should last upwards of 150K miles with no problem. The one on my 560SEC has gone 206K miles; it's been clicking for the past, say, 10-12K miles and I finally got off my duff to get the parts (and a spare flex disc, as my current discs are ~2 years old and in good shape, recently inspected). I'll have time starting with my holiday vacation this weekend to get some of these long-standing jobs DONE, and this one is number-one on my list. Will take and post photos on the C126 sub-forum, but they should be highly applicable to the E500E as well. The parts are of a near-identical design, and the process is almost exactly the same for removal/replacement.
Cheers,
Gerry
