Fix Joomla Installation - Hacked / Corrupted

We have a Joomla / Virtuemart site that was running all the latest versions. Then a new version came out and we tried to update it and there was an error with the update, so we asked our host to roll back to yesterdays backups which was fine. Then everyday we came into work, it had stopped working overnight. Generally, we could get into the admin area, but not the actual website. Then we received an email from our host, saying that the site had been compromised and used for sending SPAM, so they had deleted some files. Now, although the admin area is mostly working (left menu is missing), the front end is not showing at all. We are looking for someone who can repair the installation, retaining all the current data, design and modules etc and get us back online. You may also need to check the database etc to check this is ok.