Congratulations on your IronHorse tandem. I have an old (1990's) IronHorse single mountain bike still in my fleet. They were a solid manufacturer "back in the day." I wasn't aware that they made tandems.

My DH and I primarily ride tandems and we own three (a race tandem, a touring tandem, and a restored vintage cruiser) and just test rode what might become our fourth (a 29'er mountain bike tandem). You've gotten a very nice tandem for an excellent price and will enjoy it immensely. You did a good job to get it up and running.

The tandem forum over at BikeForums will have a lot of useful information on riding a tandem. There's also a very old listserv called Tandem@hobbes (How to subscribe: http://hobbes.ucsd.edu/tandem/info.html). Finally, there's a yahoo group called Double_Forte for off-road tandem enthusiasts.

You may want to attend an upcoming tandem rally. The Eastern Tandem Rally (MATES and ETR rally information) information is at: http://www.easterntandemrally.org
We attend the Midwest Tandem Rally annually. This year it is in Ann Arbor, MI. There are often as many as 600 tandems at this large rally.

Good luck, enjoy the bike, and let me know if I can answer any questions.