Pop it into neutral while rolling at the vehicle speed where it is hard to turn. Rev the engine rpms higher while doing this and see if its easy to turn that way.
If it is, I'd suspect your power steering pump (or rack) is shot.
But, it sounds to me like one of the front drive shaft CV Joints (probably outer) has bit the big one and is binding. Oh wait, 99 has PVH hubs, so the front axles don't rotate in 2wd. I guess one side could have failed in the 4wd mode. See if either of the front axles turns in 2wd. Jackstand both fronts, roll each wheel by hand as fast as you can get it going, and have someone turn the steering wheel. See what you can see.
I'd look really hard at the front steering components and CV Axles (if the axles are turning you have TWO problems, PVH and the bind).