Rear drive is fine in the winter, the only problem you may have is with the tires or the driver.
Parts and labour for a BMW aren't the most affordable things on the planet. However, being an older one, you can hop on the internet and find a decent deal if you look. For service work, go through an independent mechanic, like Sheni.
I find that most of those older BMWs don't sell because people still ask a LOT of money for them.
-James
Current beast: E550 Coupe (M278)
Previous beasts: AM Vantage, E90 335i (modded + JB4 Map2), E39 M5