Check out the hundreds of BMW Do-It-Yourself links. Extremely helpful and covering almost every component of your BMW. Let me know if you have a DIY that you would like on the list.
Thanks!
Here is the link to the E30 DIY section:
http://www.bimmerportal.com/diy/e30.html
Here is the link to the E36 DIY section:
http://www.bimmerportal.com/diy/e36.html
And here is the link to the E90 DIY section:
http://www.bimmerportal.com/diy/e90.html