vibration, front air bags & Front shifter
 

Hey guys,
I just bought a 98 Discovery 2 couple days ago, i am not a trained mechanic, but but have turned a few wrenches. 1st, ...the previous owner had removed the front drive shaft, dont know why. But around 50 mph I get a wicked vibration, i drop speed, put it in neutral for a sec, then the vibration stops. 2nd... It seems to me that the air bags are bad, when i push down on the hood, it is very soft, bad roll.
3rd...on the front diff shifter / lock, I am kinda confused, the manual move it to the left and right to engage or disengage then up for low, down for high, but mine doesn't move left or right. ..do they mean turn the shifter knob L/R?? Or is it like a reg manual, where the shift pattern you have an obvious L & R movement ?
Sorry for all the questions, but yesterday i broke down going to myrtle beach cost 160.00 for the tow. Pls help, need your advice, also tell me if i am posting in the incorrect forum. ..cuz i have a no start/crank question also...thanks