Learn how to work on BMWs

Sorry if this has been posted before. Any suggestions on where you can learn how to work on BMW engines and drivetrains? My mechanical knowledge is limited to older engines (ie. 350 sb) and I've heard BMWs can be tricky and a little complicated to work on. I'd like to find an older E46 M3 or something similar that could be a project car but I want to do all the work myself.

Is there somewhere to learn more about the complexities of these engines, or do you just book it and learn by doing?

I learn from BMW NA technician training and BMW workshop.

You buy a Bentley manual for the mechanic's how to of working on the car. It has torque specs and walk throughs for every project. Then you have BMW forums and helpful people who have done DIYs for you. I've learned by having a friend who was knowledgeable, a car that I'm willing to tinker on and lots of internet research.

Youtube can be very helpful, pelican parts has a good set of DIY write ups that mostly focus on e36, but I think a fair amount translates.
-durty