What is the most economical way to access repair information for medium and heavy duty trucks?

I own a small delivery fleet of 5 medium duty trucks. 3 are Peterbilts, 1 is a Freightliner, and one is a Kenworth. Can anyone tell me what the best method is to find repair information on the trucks and their engines? I would like to do my repairs in-house if I can as opposed to outsourcing everything as I have had to do in the past.What is the most economical way to access repair information for medium and heavy duty trucks?Chilton's repair manuals, not cheap, but a lot cheaper than one mechanic's visit.What is the most economical way to access repair information for medium and heavy duty trucks?Library has book and on-line