It is a fairly long process, with many steps, and not that common a DIY. After removing the trim and replacing the window itself, you will need to realign the new window so that it seals properly against the rubber weatherstripping. I doubt you will find someone who has a DIY written up with pictures.
There are DIY's available that cover replacing the window regulator, but that will only get you halfway.
Your best bet is to buy a service manuals from Bentley Publishers (http://bentleypublishers.com), or get a set of bootleg BMW TIS CD's from eBay. Both describe the process, with illustrations and pictures.
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