How do I change the information collected during checkout in MarketPress?

I'm setting up a "store" that will allow the users to fill their cart with the items they want to pick up from our real store. Ideally, I want them to be able to checkout when they're done, fill out their name, phone # and the time they will arrive at the store.
What I don't want is for them to have to fill out a big shipping/billing address form. Is there a way to alter what information is collected at the check out screen?

Even better would be a step by step on how to have exactly those three input boxes (as required fields) show up instead, if that's not asking too much.
Thanks!