When in AMS (pre-security) last week I noticed something about an Amsterdam trip that was advertised (a small stand next to a bar). Unfortunately I didn't hang around to look into it, so don't have more info.

I'd say you would have time - Amsterdam transport is excellent. I've been taking taxis (quick, but expensive - about 40EUR), but the trains are really good and there are electric buses on their own roads.. I think they might not go into central Amsterdam though.

There's a train station right next to the arrivals, so I expect you'd be able to get somewhere like Amsterdam Central in 20min or so - from there you can wander around for 90min or so and then hop back.