Android In-App Billing v3 Implementation Only

Hi, What i require is a package i can drop into my existing android eclipse projects that will active an Android in-app billing (v3) payment (single payment or a subscription). I just need the basic structure implemented so that my menu screen will have a button that says either SUBSCRIBE if subscription OR BUY NOW if 1 off payment. When clicked by the user GOOGLE PLAY asks for payment and user pays. Once user has paid i would like the app to then recognize the user has paid and forward them on to an ACTIVITY called SUCCESS.java. I can then manage the content my end. Obviously the app will need to recognize the user has paid and is SUBSCRIBED or placed a SINGLE purchase AFTER app closed and re-opened as-well as un-installed and re-installed so a MANAGED item would be best in google play, as google play can send this information back to the app without other external servers etc.. Maybe a hidden or obfuscated txt file could be place on the users phone to check the users payment information to see if he has paid before or is still subscribed. I hope that makes sense. I understand google provide a working example that can be changed accordingly, so most of the hard work is already done. Thanks