You just have to be ready for anything these days...here's a story I found interesting from the RENNlist.com website:
I had very poor experience with "Bosch Remanufactured" alternators on a Mercedes I owned for many years. Two alternator failures in less than 40,000 miles was bad enough, but the third unit had a bearing noise right from the start.
I complained to the shop that sold them. When I threatened to complain to Bosch, the owner confessed that someone in a town named Sleepy Hollow (I am not making this up) rebuilt them in his basement. What he actually did was get them working again and clean them. He had evidently repaired an electrical failure on a ~300,000 mile unit, and that is why the bearing made noise.
The units came in brand new Bosch boxes with credible-looking instructions, evidently from new or Bosch-reman units the fellow had sold. I am afraid it is caveat emptor in the rebuilt parts business. There is a lot of money there, and anywhere there is money, the scams follow.
Even new parts can fail, so buy whatever from a reputable place. If you do not trust rebuilts, go and purchase a brand new one from a Mercedes dealer. If that is too expensive, the independent shops that service the high-end makes will tell you where to get it done. Far too often, however, people balk at the price of quality work, and then seek out the least costly alternative and shop by price alone, not warranty or service. And that is where the trouble begins!
I had the alternator replaced with a remanufactured unit in 1999, not a problem since. The starter was rebuilt locally too, but caused problems that we finally sorted out. May you just have good luck with the endeavor!
You also can, if buying something over the counter, inspect it right then and there: if you see things you don't like, get a different box. If that offers a marginal looking product, try a third. If you are not satisfied there, walk away.
Local places will not "remanufacture" but rather "rebuild" alternators. Aside from fixing the obvious broken parts, you can tell them what else to do. Maybe you have a Pagoda with 300K+ miles on it; new bearings might be in order. The only challenge you might find is if your alternator is totally trashed the cost to rebuild might exceed the cost of a reman unit. Let's hope you do not run into anything like that, but if a screw or foreign object got inside, it is trashed.