you should have done a search in the forum and looked at the DYI's, unless you are very good at working on your car i read it's not recommended to do it at "home" , those bearings are PITA to take out, and you will need to purchase a special tool (if you want to make your life easier)that can run into 300$ or try and make your own home made "extractor" as some have done.
back to your question, there is plenty of articles and DYI's in the forum just use the search field
for rear bearings, the procedure is no too different for most BMW's...I think.
P.S. taking it to a shop will run you couple hundred for each side.
Bav Auto has the tool
,$250+ choose your year model and pick tools, it should come up.