enable in app billing for previous code provided for the agreed $40. Fire up eclipse and open the appMainTesting and load the android Id etc to get it going. Send code back to me and I will upload since I have the keystore for that app. Then after I upload to developer console you can make tests.
I have developed many games for my company, and we use a in-app purchase class (written by my self). I can easily combine it with your current project.