Also, those big guys are so tough to do business with. They've got many-a-corporate-layer. I have no idea who I would talk to about something like this (without connections there).
Search Linkedin to find emails or just cold call.
I would suggest getting a strategy together to do this, just like you had a strategy for the business.
For example:
Identify possible buyers:
The large players, Edmunds, AutoTrader, etc;
Large dealerships - they might want this for their own inventory, it seems like it could be easily adapted for a dealership. Concentrate on finding dealerships in large metro areas. They sell millions of dollars worth of cars. Places like the tri-state area, virginia/dc/maryland, LA, Seattle, Texas, etc. Get a list, find some emails, put it together.
Car companies: email them all. They might want to buy your software to showcase their stuff. Its very clean, and they can adapt it. Email the ones out of America too. China, India, Europe;
Identify the people in the organization who will buy. Spend a day researching them, put as many emails down as you can find. Be clear about what you're selling, and how it might be useful to that organization. Get a spiel together for emailing car companies, dealerships, etc. Show how it can be adapted to their needs. Every email you get, its like raising your price. Go after this selling thing like you went after building your website. With gusto.
Hold an auction on a certain date, and ask that bids be submitted.
Don't worry about the lawyers for now, they'll get involved when a buyer is actually interested. Until then they stay out the picture. So lawyer involvement is a good sign you've piqued some interest.
