I just purchased a 2003 x5, 3.0, and it does not have Rain Sensor or Auto Dimming mirror. I was wondering if I can replace this mirror with a Rain Sensor, Auto Dimming mirror? There are a few for sale locally, and all I really need is the Auto Dimming feature (compass is a good value add), and dont really need the Rain Sensor. Can this be done? Thanks!!

No you can't, the actuall sensor is on the windsheild not the mirror. It would also require new modules for the lights, possibly new head lights, a new light switch and maybe even a harness.