first off, i don't know where you live but the charge looks like its a little high. i would expect somewhere south of $400 but if you live in a metropolitan area, that may be the going rate.
As far as if its necessary or not. If you plan to keep your car past 100,000 miles i would definately say go for it. The transmission will probably last to 100,000 without a service, but not far past that. As far as changing the oil, bmw's every 12-15k is junk. Until bmw started their "free scheduled maintenance" stuff they recommended oil changes every 5-7.5k miles and transmission services every 30k, now its "lifetime fill". Nothing changed but who picked up the tab so they decided that you could go a lot farther. This is simply not the case. i recently replaced the engine in a 2001 330ci with only 68,000 miles on it because bmw's maintenance schedule had been followed and sludged the engine up to the point that it clogged the oil pump pickup completely.
i'd say that having the services done would be a good idea, but i think i'd call around and get a few quotes first!
ASE Certified Technician
8 years professional experience, Have owned 30+ bmw's