Hey, chaps, in all seriousness you MUST have a crack at spins if you get the option. It was mandatory on my PPL course and is the most fun you can have in a light aircraft (with the obligatory clothes on).
It can be scary at first when you're just spectating but when you actually get hands on it's REALLY entertaining. You should make the most of the chance while you have it! (and it will liven up your instructor's day too). It's actually a relatively gentle maneouver and is a LOT nicer to practice than pulling G in Spiral Dive recoveries, despite what appearences suggest. Go on, live a little, you can NEVER have too much knowledge of how aircraft handle in different conditions!
Re: Stalls - it varies a LOT between types. As mentioned by others, stable aircraft like Cessnas and Warriors (and a Katana, from memory) have very, well . . , dull stall characteristics and it really is nothing to worry about. There are no dramatics to catch you out. Something entertaining like a Tomahawk can present more of a challenge but hey, you've got someone experienced sitting next to you and you're there to learn confidence in all situations.
You'll be fine!