Additional Gateway Integration into Prosites Plugin

I really, really want to use the pro sites plugin, but I need it to integrate with Infusionsoft. I am happy to write the integration, but I am wondering if you have any tips for me. The easiest way I am thinking would be to integrate URLs that GET data - Infusionsoft can post data via a URL on order completion, order failure, and other actions. If we could build methods that would accept that info and then trigger the right action - account creation, account suspension, etc that would be awesome. I don't assume that you have an API of any sort for this plugin, but can you give me any pointers on where to start for an integration like this?