Simple Search form with a few drop-down choices
I would probably create some categories for make,  color and transmission and relate every entry to it. Then you have the ability to use craft.entries... to fetch the entries as you need them. You can find all specs of the entries method in Craft's docs -  just fetch all entries that are related to the category you want. 

Depending on the total number of entries you could just fetch (and cache) all entries every time and use a javascript filter mechanism. I worked with isotope before.

Using js you can achieve a smoother UX once all entries are loaded. However, best practice would be to start coding without js and make it work and then enhance the experience with js. Depends on your budget.