Hello,
I am experienced PHP and Python developer. I uses WHMCS since version 5.0. I'm using WHMCS 7.5.2 now (will be upgraded to 7.6.0). I have created WHMCS Provisioning Modules, Payment Modules, Addon Modules and WHMCS Hooks.
I can help you upgrade your WHMCS to the latest version. Let me know if you're interested.
Regards