Create iphone app - clone of an existing app

I need an iphone app created for my ticket website. there is already another iphone app created that I want to use as the guideline. If we can take everything from this app entirely and just modify a few things to customize it to my site that would be ideal. Please contact me, and I will share with you the name of the free app, so that you can download it, and figure out if you will be able to take the app and modify it to make it my own, or if you will have to create the app from scratch, you can still give me a price based of the existing app.