fixing a hacked site?

I was wondering if someone might be able to help me. My blog seems to have been hacked. I had redirected the site to point somewhere else but have removed that you can look at it (techblawg.ca). They’ve put up a silly looking page, and have reset my admin password for logging in.

I host it on a service provider (Site5) and only this and another site under my account, both using wordpress, have been hacked. The other sites I have under the account seem to be untouched.

Unfortunately I’ve not dealt with this before, so I’m not sure what the best way to fix this would be. I’d very much like to retain what I had (to the extent possible without compromising security), but should I instead just wipe everything and reinstall? If I wipe, should I just erase all files starting with wp- in /public_html/? Do I need to delete the database files separately?

Any suggestions on how to get it back up and running, and, if anyone is able to tell, what I could do to beef up security (and in particular what happened to allow for this hack) it would be most appreciated.