Hi
I can sort this out for you. I would use a php based shopping cart and integrate that with paypal payments (as long as that is what you want).
I have made the bid at $475 which is veyr low, but i want to be within your budget.
I will be available over skype and msn. If there is any other form of IM contact you would prefer, let me know and that can be arranged.
If you let me do this, i will have it done within 1 week (i have put 10 days on this, just incase you want some things changed)
Hope this is good for you :)
Matt