nothings impossible. i personally would never buy beginner gear in any sport i want to learn. the idea of being stuck with crap equipment when i get comfortable after a few weeks and having to drop a tun of cash on gear for a second time scares me. plus i like a challenge.
keep the board and try it out like the shop says. from the sounds of it you got an awesome deal on a great board. if your that worried about progression i would keep the new board new and grab a used beginner board off craigslist or whatever you have locally. one of the problems or benefits (depending how you look at it) with snowboarding is 2nd hand gear has almost no resale value. brand new last years models sell for around 1/2 off making used gear worth maybe 25% if its in good condition.