Joomla/Virtuemart work

Need some modifications to our online store- Joomla/Virtuemart Requirements 1. Creating a scipt for external shopping cart button. This script will be to allow contents of the external cart to be added to my own cart- see attached document for details. Also to create a process in virtuemart for accepting items from external cart. 2. Customise product page to include tabs. 3. Create pricing module. More advanced than the basic attribute pricing. Want to be able to recalculate the customers product price based on, customisation chosen and quantity. When the customise product option is selected on product page - a popup (AJAX or something similar) should be created, customer chooses location/s, customise method for each of the chosen locations and the size. This product module should then work out newprice of product to include customisation. 4. So SEO modifications and possible 1 page checkout. Will require documentation and files. Want to have the modifications if possible as plugin/componet etc so that they are easy to reinstall(in case something happens to my own joomla I can then reinstall as necessary). Please contact me if you need further details of my requirements. There is no urgency on this project 1 week to 1 month. And thanks for bidding.