PHP script - modify existing PHP Pay to Download script to include Google API for Powerpoint conversion to Google Docs PPT

Need someone to modify existing PHP script. I purchased 2 PHP scripts. [login to view URL] [login to view URL] Both these scripts allow visitors to pay money using Paypal and then be able to download a file. What I need modified is adding: 1. User login and credit system 2. When uploading files, it'll need to be converted to Google Docs format. So I upload a Powerpoint PPT file, it'll convert to Google Docs file and allow me to download that version instead. 3. Allow multiple file uploads and ZIP download You do not have to worry about design, colors, icons. Just get it to work with maximum security & AJAX. Please use Twitter BOOTSTRAP as HTML/JS framework for everything. Budget is $150 and must be done with 2 weeks.