What you need to do is plan exactly what you want and then start learning how to create a database driven site. PHP and MySQL are great because they are available under the GPL and great for a startup.
But you really have to know what you want out of the site. When you know - it is time to grab a couple of books and start posting in the right forums. But I can't stress the importance of having a business plan and an exact idea of the processes that you want. Forget about asking at this point if it can be done - just assume it can be and start from there when you create your business plan.
I need help, but I think I'm beyond help.