The most important documents that you should have are the repair orders that you are given after your vehicle has been in for repair. Each time you take your vehicle in for repair you should make sure that all the information contained on these documents is correct. For example, you should be sure that all the complaints are written up EXACTLY as you have stated them; that ALL of your complaints on that visit are included; that the “dates in” and the “dates out” are correct; that the mileage is correct; etc.
You should be able to get your repair history directly from the authorized dealer(s). If you cannot get them yourself, a qualified attorney may be able to issue a subpoena to the dealership to obtain all the documents on your vehicle. Also, if you keep a calendar of appointments which shows when you took the vehicle in to the dealer, this can be helpful in lieu of or in addition to the repair orders.