Hello :)
I am interested to help you with this small task. If I understand you clearly you'd like to insert in-app-purchase. If you have some additional features to do, the price will be changed. I garantee high quality of work and will be glad to help you with the publication on GooglePlay (if you have no relevant experience). But anyway we can discuss all details by chat. So text me if you have some questions :)
All the best,
Anna