Multiple Category Drop Down search

Hi there,

I’m looking to implement a drop down category search in a site with a vast catalog. I’ve tried several solutions but no one really worked in the way I need it. The site is designed to manage an auto-parts catalog, organized on the following structure:
(MAKE)->(MODEL)->(YEAR)->(ITEM)
Actually the Model is a child category of the Make, but the Year is a separated category. Also, all the Make categories are child of a category call “Make”.
What I need are three drop down menus, on the first I will be able to select the Maker (which will be a sub category of the parent category ‘make’), and then once the first drop down is selected I need to display on the second drop down the child categories of the category selected on Make. Then I have a third drop down with years. On the submit action I’ll need to perform a search to find the items matching the three selections (actually with Model and Year should be enough).
I’ve been struggling with the exposed on this posts:

http://wordpress.org/support/topic/is-the-new-dropdown_categories-working?replies=13#post-657759

and

http://wordpress.stackexchange.com/questions/10570/multiple-level-category-drop-down

Some of these solutions worked partially, but not exactly as I needed. I know that I should implement JS in order to “capture” the action on the first menu, and pass that info to the second drop down to display the child categories.
I need also all the three menus displayed from the beginning, with the second one empty (showing “model”) until I select a category on the first.

Here’s a link to the site I’m working on:
http://www.sofiajuan.com/broadfeet

This is a site with exactly what I’m looking for:
http://www.blackhorseoffroad.com/

Thank you very much!