Have you ever tried?
It's actually pretty easy... or at least I've never had a problem with it.
I tell the Sales Rep up front that I want to buy an item, I'm fussy, want to inspect a machine before I purchase and, if it's suitable, will buy the machine I looked at.
If they can't/won't oblige I have no problems walking out the door. After all, if they won't help ensure that you're satisfied with your initial purchase, what do you think their after-sales support is going to be like?
(FWIW, this is my philosophy for any machine I'm spending more than $500 on... unless for some reason it's so cheap that it's a bargain even if broken. :shrug:)