Change Website Phone Number on AdWords Click

This is a fairly simple small project where I need to have the phone number on a website change when the user has been directed there from an AdWords click. This will require the creation of a cookie which will record whether a visitor came from an AdWords click (URL contains 'gclid') and then a modification to our site so that when that cookie is present the phone number that appears in the top nav is different. Here is an example of how this will need to be done. [login to view URL] The winning bidder will receive access to a development environment of our website to do the work. Once the work is complete we will then move this over to our production environment - you will need to clearly outline what files were modified and what files need to be added.