I just replaced a starter - not a big job. First, remove the gas tank. Second, take off the air intake and filter. No need to remove the underlying filter box. Two bolts hold the starter cover on. Remove them, and the cover lifts right off. If you are removing the starter, there are two bolts and nuts holding it on and a bracket at the rear if it is a Bosch starter, or just two bolts if it is a Valeo starter. Use a 13mm 1/4 drive socket with a 1/4 drive breaker bar / flex handle to get the bolts/nuts off. See the thread "Diagnosis Please." If you decide to replace the starter, do not buy it from a BMW dealer, but see the link in the "Diagnosis Please" thread -- it is the same starter and will save you a lot of money.
k_enn