I am (among other things) a Microsoft Access programmer. If you pruchased Word, Excel, Powerpoint from Microsoft chances are that it has Access included as well. Access would be a wonderful tool for building a database to keep track of customers, store photos of their car, print reminder postcards, basically anything that you can dream up. In fact the BWCI link that was posted earlier is an Access db (and specifically set up for animal vets so it won't work for you).
You could hire someone to build the db to your specs (probably cost around 1K for a really nice interface and lots of goodies) or develop it yourself. There a several very good Access forums (I participate in a couple) where you can get a lot of FREE help with your application. Take note that development of such an app would take (done in off time) about 4-6 months.
I'll look around for any pre-developed apps that might fit you needs.
Autoeng