To make a long story short I found the offending code, which had taken up residence in the darkest, dustiest corners of my server, and apologized to google, then got my site up and running again. I’ll list the sites that I found useful below rather than regurgitating their content:
Details of the actual hack:
How to fix it (make sure to read users comments too):
MediaTemples admission of wrongdoing (kinda):
And their version of how to fix it:
Hope this helps anyone experiencing the same problems.