Mods to admin panel

We need an experienced coder to make the adddition/mods to our existing script as per attached mockup. We want to have 'subscriptions and coupon' functionality added as it can be seen on our mockups. We need also the fron page 'subscription.png' coded including the PayPal feature/access using Paypal's 'sandbox' feature.

The existing script is 'open source' and not encrypted and can be viewed by potential bidders.

It must blend in with the existing script in design and style (CSS style sheet are
for multiple display schemas )
The MySQL database is already existing and has to be altered/modified to suit the new functions. The script is coded in PHP and has to run on a Linux web server.
The awarded coder has to install the mods and test it before final payment is done by us. We would like to use this website's escrow fecility.

We can give full access via FTP to the files and full access to the DB via the phpAdmin application but unfortunately not to the CONTROL PANEL.

Please do only bid if you have good coding experience and done similar work before as we value good file housekeeping and good quality of work.
Please honer the time you give for completion of this project as our progress schedule is adjusted for that timeframe.
After successful completion of this project more work is available.