I started a expedition i thought a fried was gonna join me in for some reason i never seen or heard why was supposed to be co-op. Can i invite a friend to the expedition i'm in? Or start an event in community for a player to join? Because i'm stuck in this one i can't finish. And the game don't let me back into the world even when i quit, close application and restart game. If i cant invite someone then what do i do? I'm hoping i can just invite or community event.
As AgentSeta said, you can select Abandon Mission and it will spawn you back to Prosperity.
And no, you cannot change your "party" (so to speak) while you are in the Expedition, because technically Roger flew only you to that distant location.
That's why you cannot change your Gun For Hire or you cannot invite a friend.
However, if you invite a friend in the normal game and then start the Expedition (while your friend is in your game), you will both travel to the Expedition and can play it together.