Add More Functions

I have a basic shopping cart that I need a couple of functions added to it. 1st. The cart already allows for upload of a screenshot through the admin panel and shows the thumbnail on the front end as it should. I need for there to be the option under the thumbnail for a link to where when a user clicks will show the full size image. (the script thumbnails the image automatically)I just need the link on the frontend under the the thumbnailed image. 2nd. I would like for there to be a field added to the admin panel that allows for me to imput a URL to a demo product, and this url should say something like "Demo Here" will open in new window. This should also show on the front end to where the customer sees the product listing. This cart is written in PHP and uses mysql as the backend. It also uses templates (php templates with html tags, etc.) I need this done asap. You can see a working demo here: [login to view URL] with the admin panel here: [login to view URL] user/pass= test