Strange that -
I actually just logged on because I remembered I hadn't answered that part of your question.
I don't know. Orbiter isn't set up as a multiplayer platform, but I'm pretty sure there are several people (teams?) working on that, but honestly, it's not something I've really paid attention to. Hopefully someone looking at this thread will have a better answer for you.
So, I'm going to throw a little unsolicited advice your way since you're going to leap into this one way or the other.
There are many excellent addons available, and while not as pretty as some of the ships and stations, the MFDs are going to make a huge difference in the success of what you'll attempt.
Here's a couple of 'must-haves', at least for me:
IMFD by Jarmo Nikkanen. The Interplanetary MFD (v 5.1d?e?). If you want to get from one planet to another, this is a good one.
TransX by Duncan Sharpe. A sophisticated navigation tool. I'm still learning this one, but seems to be more appropriate for planning trips to the outer worlds. It's similar to IMFD, but more advanced.
Though not an MFD-
AbsoluteKillrot by Enjo. Time compression is important, as it makes Orbiter doable. The stock kill rotation function of Orbiter you'll find lacking when running in 1000x. Enjo's addon makes it a lot better.
I just remembered there's already a thread here about what I'm offering, so link to this one:
http://orbiter-forum.com/forum/showthread.php?t=16