I will make it in 4 pages, Home, Solutions, Problems and Jobs.
In the Home page you will have the 3 pulldowns, the 2 search bars, a side bar with links to the problem cars, and another side bar with the job opportunities.
In the Solutions page you will have the previously posted solutions to the problem and a button to add a new solution. The new solution will be in a step by step format, with the possibility to add a video solution, in a video hosted on your page, not youtube or anything.
In the Problem page, users will post posible solutions and the person who posted the problem will be able to mark a proposed solution as a the answer to the problem.
The Jobs page will be a page with descriptions and contact information for the posted jobs.
I'll use Twitter Bootstrap, JS, and PHP/MySQL or ASP.NET/Microsoft SQL server.