126787 Shopping Cart Export / Import

I'm considering changing shopping cart scripts but would need to export all customers and transactions out of my current system and import into the new system. I can show you the fields in the message area if you like but am looking for someone with some experience at doing this who could get it don't for just about any two carts. There will be only around 12-15 products and they will be entered into the new cart system manually by me. It is a digital products cart so I need to make sure all the same customers have access to all the same products and can log into the new cart with their old email and password.