Hello,
I went through the description, and understand what you want. I am well experienced in web APIs, XML and JSON.
I think it should be involving a single API call. I will be able to finish it in 2 days.
I am keen to do the project. Please have a look at my previous projects - most of them are API related. If you have any concerns regarding time & money, please let me know.
EDIT : I think it will be a good idea to integrate a map. The user can search for his location, and the address & zipcode will be directly found with Google Maps API.
Thanks,
Vayne