I'm a rower on my school's team, so a bit of insight: the rowing machine is really for one thing, rowing. There are plenty of great workouts you can do, anything from long steady state to high intensity intervals. But if you're just starting out on the erg, you have to commit to learning the techniques and fundamentals of rowing. Not to turn you off from trying out the sport, but to tell you better what you're getting into.

If you're still interested, start by googling some tutorials on erg technique. You should be able to find some good videos from some respectable crew teams. For workouts, you can do anything from pick a preloaded workout on the machine, to googling "erg workouts" or something. I think concept 2 (the company that makes the machines) has some good exercises on their site.

PM me for rowing questions if you want, and welcome to the club!

PS I second nemo. If you want to get generally fit, do SL 5x5.

What do you play? Oh, I play the traffic-coneophone