Definitely go to a different dealer. You should be able to try every operation that the machine offers (or at least every operation that you intend to use). Sometimes the dealer will just let you play, sometimes they will sit and give you a demo then say "ok now you try" and remain there with you .. but either way YOU should be the one controlling the machine.
Additionally, if you were interested in purchasing a used machine, you should try that specific machine, not just a new machine of the same model.