Just browse around using FileZilla or something. On the local side, have a fresh download of your version there. On the remote side, view your wordpress blogs? Go through every folder and make sure their aren't any shells or extra files that look fishy...
OR, just backup everything, make it like blog(old) so you have the old blog in case you need something. Also, don't remove the databases yet, make new ones. Long passwords. Longer table prefixes as well. Just don't install themes that are 'custom' because they may have a shell on them. This is what I did when I moved my blog, to a different subdirectory and subdomain for simplicity. I do things the hard way, so that I know their done right. Also, I don't have blogs that make me money lol. This is a blog I designed for a different reason. Basically for my PC repair business.
Change all passwords as well. FTP. Your hosting site, if you can. MySQL databases as well. I hope you're fluent in doing this. I mean like editing all the wp-config.php files to put your new database password in? Even if you make new blogs and transfer everything, still - change the OLD blogs MySQL passwords just to be safe. Then, give me your website and I'll see if I can get through. ;P
Too bad their isn't a program where you can open EVERY .php and .html file, and see what is displayed. Then, you can see if there any C100 or C99 shells. I'm sure they have some MySQL shells because, the MySQL shell on C100 shell kinda sucks and doesn't work all the time. IF they were smart enough, they would have grabbed the MySQL password and username from the config file, and saved it to make your life miserable, because they know people will only delete the index.html file and move on.