Extended maintenance? Don't bother - it's probably going to come out about the same either way since it's fixed and predictable.
Extended warranty? Now that's personal preference, which needs to factor in how trusting you are of the car, how long you want it, and how willing you are to DIY if things break. I haven't decided on extended warranty yet, but from what I gather I still have time (up to 45k miles before the cutoff).
If you do extended warranty, make sure you get the BMW FACTORY extended warranty, not through the dealer, not through a 3rd party. More info
here. Prices you'll have to google - plenty of threads on that.