[dmatre]

To save you some time:

General Info: http://www.e90post.com/forums/showthread.php?t=352586
More General Info: http://www.e90post.com/forums/showth...ght=door+wires

Underseats: https://dl.getdropbox.com/u/47031/BM...%20-%20PDF.pdf (with Ken's kit, no need to cut - he supplies spacer rings)
More underseat info: http://www.e90post.com/forums/showth...hlight=install
More underseat info: http://www.e90post.com/forums/showthread.php?t=586892

Doors: http://www.e90post.com/forums/showth...hlight=speaker
More Doors: http://www.e90post.com/forums/showth...hlight=speaker

My experience: http://www.e90post.com/forums/showthread.php?t=581379

Buy/borrow the plastic pry tools - do NOT try to improvise here!!!!

It's not too hard, and the reward is well worth the effort.