It's definitely a great way to get to know people well if you don't, as you're awfully close for ~30 hours.
I've done all of them with a running club at work. The first time we did it it was one team, so I knew everyone really well, but it's ranged from this last NH where we ran 3 teams (6 vans) and I had a lot of people I didn't really know well at all, to years where we ran 7 teams / 13 vans, and it was half the company there.
A lot of the time I've been with at least one person I know really well, but often at least a few that I may know a bit, or know of, but not personally. A lot of it comes down to personality: super uptight people aren't going to do well with the small annoyances that can pop up 20 hours in when no one has slept and they can't find their wet wipes. But if people are chill, that's not a problem, and you'll likely end up with pretty tight bonds driven by the ridiculousness of the entire thing.
You're spot on with the distance not being the issue: if you're trained for a half, that's basically the base that you need. Generally, though, we'd do hills at least once a week, because the NH RTB course is super hilly. I'm not a huge fan of double sessions in a day- I find it causes me more grief than benefit- but it's something to consider to work in once a week or so, to get used to running on tired legs (or, perhaps, a night/morning session). It's a lot harder than a half, as by that 3rd leg you can be a bit blown out, but a lot of depends on the legs you get. Some races have variance from sets that are ~22 miles of very hard/hilly legs, down to ones that are ~14 miles of easy trots.
Really though, the hardest part is coordination and logistics. It gets surprisingly and awfully hard to manage everyone's shit in a van (oh, also, rent a van. I always feel really bad for people who do this in SUVs or something. 6-7 people take up a lot of room). Staying on top of trash ends up being big.
I think the single best tip I ever got was to have everything I need for each specific leg in a numbered gallon ziplock bag so I don't have to think about it when I'm frantically trying to get ready so I have time to get to a porta potty and actually be at the handoff when the runner comes in. Not being able to find something in the van is the worst (hence why managing garbage/clutter is key). Have separate ziplock bag(s) for toiletries (deodorant, wet naps, etc) in a grab bag along with anything else you may need on hand that you can keep closer to you, while the rest of your stuff is in the back.
Oh, also: get a Stick. Use your Stick. Love your Stick.