Design Updates for existing Phonegap App

We have a current app for Android and Iphone that uses phonegap. This project is to Work is about 70% design updates, there will definitely be some javascript changes to be made to update to the new design. I will be sharing the current code base and api. The end result should be a bug free app, code changed pushed to our repo, packaging them for iOS and Android store. There will be a 30% bonus if they deliver