I think the factory service manuals paper are first choice. The cd's I feel are frustrating at times, because they are blurry in print in places and the photos are very blurry and vague, but it's a cheap way to go. You can get them for under 20 dollar. Especially, trying to trace the electrical circuitry. My second choice would be Bentley, if they make one for your particular car. In the third choice it would be probably be Mitchell and then Chilton. My last choice would be the Haynes. I think, maybe that Haynes has merged with Chilton now, but I am not for sure on that? It's kind of personal preference, but I like to have a book with me by the project. It's nice to be able to work back and forth right there if a reference or a torque is needed etc.