You have to edit the style.css file for the templates you use.
Your best bet is to copy the 'portal' folder found at whmcs_root/templates/portal and rename it somehing unique.
In the clients area, underneath account information it says add funds.
[noparse]http://www.yourdomain.com/whmcs/clientarea.php?action=addfunds[/noparse]
I raised a support ticket with them and they said to ask WHMCS as they developed the module.
As I said the domains are already registered and with Heart, so I can't see why there would be a problem
I'm using the HI Modules.
When I go to test the system, I tell WHMCs that I'll change nameservers etc and enter a domain that is registered with HI but the account never gets created, I get this error message each time.
Module Create Failed - Service ID: 3 - Error: The domain name is not available for setup