The drop down script requires jquery-1.3.2.min.js and jscript_model_year.js

The styling script requires jquery.js and jquery.jqtransform.js
The drop-down requires jquery, it works with jquery version 1.3.2 and I am currently using it with 1.82 so I would assume it works with all versions inbetween.
You just have to load one version of jquery that will be used by any other scripts on the page.
Look at the start of the jquery code to see what version it is.
It should be loaded before the drop-down...i.e. if you have moved the other scripts to the bottom of the page, the jquery call must still be at the top.