If your current app is convoluted, then now is a good time to rewrite and streamline it. I printed out the code for all of the last channel upgrade I did and went through with a sharpie crossing out code that wasn't used. It saved a lot of headache. Basically, any UI screens need to be recreated - if you used roScreen/roImageCanvas then that's a lot of work - if you used the default posterscreen or gridscreen then it's easier. Also the video component changed so that will need to be recreated, and the springboard screen needs to be recreated, and the linking/billing routines might need to be recreated. Take it screen by screen, take your time, get one part working and test it, and then move on to the next display.
For JSON parsing, here's some code I threw on GitHub. It's not a complete application, don't have time right now for that, but hopefully this helps.
https://gist.github.com/timbeynart-nbcu ... 8c104f82af