Also, is it a reasonable assumption that it's expected for a match attendee to have some experience in working the pits before attending a match?
Not really expected--you've got to start sometime (I suspect lots of people pull for the first time at a match) and it's really not that hard, but you should do some reading in advance so you know what's expected of you. The rulebook covers the procedures, and there are a bunch of good web pages as well. (If there are four relays, you'll have two people on your target in the pits, too, and you can get on-the-job training.) 99% of the time it's just "remove the spotter from the old hole and paste it, put the spotter disc in the new hole, and (maybe) move the scoring disk to indicate the value of the new shot".
Also realize that competitors have three jobs--there's shooting, there's pulling targets, and there's scoring, which means sitting behind the shooter with a scope and writing down the indicated scores on the shooter's score card, as well as keeping an eye out for various safety and procedural issues. Scoring correctly is at least as important as pulling targets, if not more so.
Aside from NFGA, there are also periodic clinics at Woburn Sportsmen's Assn and Mass Rifle that will give you a gentler introduction than a match. (Are there other area clubs with pits that I'm forgetting?)
Reading has a bunch of really serious rifle shooters, but they're also very helpful to the first-timer. I shot my first XTC match there, and while I probably made every mistake in the book nobody bit my head off. (I did get asked by the pit boss to take it easy getting the targets up and down, then got asked by my shooter for faster pit service, though. Sometimes you can't win!)
Good tutorial (in three parts) on scoring slow fire in the pits:
http://www.youtube.com/view_play_list?p=668F7FE5E77137D4
Scoring at the pits at the Nationals at Camp Perry:
http://www.youtube.com/watch?v=5-binhN91uA
Rulebook:
http://www.nrahq.org/compete/RuleBooks/HPR/hpr-index.pdf