I would check your credit just to be safe. Secondly if they did I would send them a nice letter saying that you were going to take them to small claims court to get back the money you paid for work they did without your permission. If they didn't report it on your credit then i probably would drop it and part ways with the dealer.
Like you I try to do as much work as I can. In the future you should be able to search the internet to find out how to do the tests that require "JD" or other brand equipment. My newest battery charger can do a complete check of your charging system.