Sites hacked, need advice on recreating reseller account

Hello

My reseller account recently got hacked (cheers guys :D) many of the joomla sites on the account were accessesd and passwords changed, I am assuming all sites compromised beyond my knowledge and must start again. I am looking for advice for the safest and best way to do this without having to wipe all out and start again. I know I must delete at some point but I want to do this with minumum downtime over a period of weeks. Is it best to get a whole new acount and create new sites then change nameservers or is it best to reuse same accout, if so I cant figure out how to build a new version of the site when the hacked version is still live?

Any help much appreciated, thank you