Css layout changes

We have designed a box slider for a form at the bottom of the page as you can see on [login to view URL] When the fields are completed on step 1 and step 2 and when we go to step 3 and click on previous to come back to step 2, the next and previous buttons disappear. The height of the box needs to dynamically change as an optional extra field comes up when all the fields in step 2 are completed. The optional extras box height changes with each car as each car has different optional extras. To understand what I am talking about, try it out on the site. We need this fixed in the next few hours, please bid only if you can get it done today and if you are confident of doing it. To reply to this project include "bananas" as the first reply, generic replies will be discarded. Thanks for your time.