1. I don't use an alarm or have lojack.. just make sure your car is always locked.
2. It depends on how much snow you're driving in, personally I think the DSTC is good enough but again, personal preference.
3. I tend to do all mods with the dealer or Bavarian Autosport.
4. Maintaning the engine has never been a problem for me, I just start it up and go.
5. I use turtle wax to protect the paint of mine.. any good wax will do it really.
6. Good choice buying a BMW.. the best car maker out there!