absdigital on "Creating a custom search form - using custom fields and custom post type"

Here is what I'm trying to achieve.

I have the HTML for the form there but how to implement it into WordPress is driving me nuts. Make, Model and Price are all custom fields entered for each vehicle (each vehicle is a custom post type).

I need all the available Makes to show in the drop down list and when one is selected have it function as searching for posts with the same Make. And obviously the same for the Model.

The price I'll worry about after!! This is doing my head in big time, any help would be massively appreciated!!