Hello,
I am used to work with WHMCS and did the integration for Webdomain.com.
If you give me more details about the modification, I would be able to scale my offer accoringly.
I am available if you need to discuss the details of your project per chat.
Concerning the templates, I can't unfortunately give you the one I did for other customers, but I can easly customize them for you.
Let's discuss about it per chat.