Hi Laura,
Welcome to the Den! That is a nice looking Eagle you picked up.
When you say its is in 4WD, is it the switch that is in 4WD or have you confirmed that the transfer case and front axle are in 4WD also? I believe that if the proper vacuum hoses aren't in place that the car will revert to 2WD. I don't think there will be any issues driving it that way, but sometimes if the transfer case isn't held in either 2WD or 4WD by the vacuum pressure, you may get a false neutral, which means the transfer case has basically slipped out of gear and you can't go anywhere until you move the lever manually into 4WD or 2WD.
Best of luck with fixing it up, and don't be afraid to ask questions!