You might be able to take a look at the code here:
https://github.com/dealertrend/wordpress-plugin-inventory-api
DealerTrend has their own WP plugin but I don't remember what it looks like or how much you can do with it. You could take a look at some of the source code here though. I imagine a lot of the actual manipulation would be on the front end though.
Have been talking with them for awhile now, if they can code my design for me then it will work. Just sent them an e-mail today with my finished designs. Their layout/features are really similar to what I need, just big differences in appearance. If that doesn't work I might end up hiring a PHP programmer to get this project done for me since I don't have enough time.