i plan to order a full set of mounted tires/wheels for the winter. BMW seems to want a lot of money each season for putting them on the car... which i know is a relatively easy process that i just don't feel like doing myself. (maybe i should).

Some of the 'local tire stores' offer free winter tire changing and will put them on my car absolutely free. this makes me a little nervous... is there any specific knowledge needed on the new x5's?

I'm thinking of ordering the package from tirerack, which has the sensors and everything installed before shipping. anyone used this? do these sensors work properly for tire pressure monitoring?