Need help with some security issues on Wordpress site

I have a few issues with a Wordpress based website that I own that I need fixed, and they are beyond the scope of my limited expertise. Here is a list of the issues I need fixed: 1 - I installed a plugin called WP-Supercache, which is a caching engine for Wordpress. I was not happy with the result after installing it, but I cannot get it uninstalled now, I am getting a variety of PHP errors when I attempt to disable or deinstall it. 2 - Someone has hacked my site. It looks like a SQL injection exploit or something. All of my pages and files now have some shady looking encrypted code implanted in them above the header. They look like this. <? /**/eval(base64_decode('aWYoZnVuY3Rpb25fZXhpc3Rz........ It's come kind of keyword spam all the keywords relate to things like "forex trading", which has nothing to do with my site and someone obviously put there on purpose. I need someone with experience in this kind of hack to go through and remove the malicious code. 3 - I need someone to "lock down" the site to prevent this from happening again. 4 - I need someone to take a quick look through all of plugins I have installed and advise me if they should remain or are of little value and should be removed. The domain I am having issues with is [login to view URL] and it is hosted on Bluehost.