Billing Module

I have a membership based website that was created using Post Nuke CMS. I need someone to choose and install a secure billing module on my website. It will have to work with my [login to view URL] account. Currently, I have an older version of DreamCost installed, and that will need to be uninstalled. Using an updated version of DreamCost would be ok. The billing module must be SECURE though and must be formatted to match the theme of the site. In your bid, please explain which billing module you will use and include any software or code cost in your bid. Thanks. Good luck bidding.