A while ago I took over support of a web site designed using Joomla! Last Friday the web site was hacked. When I contacted the ISP I was told "we don't support Joomla! sites". I tried doing a restore that failed and contacted the ISP again. This time he ran a scan on the web site for malware and gave me a list of files I should remove. As that list was pages long I gave up on that. Our President got email from sitelock.com telling him that the site was hacked and offering to help. Apparently that is a legitimate company.
As of now I haven't done anything else. Does anyone have any suggestions as to how should proceed?

Thanks