Create Phpfox add-on with Android app development skills

I need someone to install phpfox onto my site and also some add-ons. I will also need someone create a type of For Sale bulletin. The add-on will incorporate Google maps so that buyer can know the distance they are from the seller. The add-on will also allow the seller to post picture and video of the item. On the sales page of item, there will be Facebook type social media communication with seller and potential buyers. Please let me know how many hours it will take to create this add-on. After the site is completed, I will need an app created based on an existing app that needs modification.