Without a hoist getting at these switches is just about impossible unless you have four hands - even when front wheels are on a ramp. Make sure the dirt has been cleaned off the T-case or it will fall inside when the switch is removed.

If I remember the switch has one wire to it and the circuit is grounded through the body of the switch. If that's the case then you'd test by touching the wire contact and the switch body for continuity as you press the plunger.

92 Montero LS 3.0L V6 Auto, Stock, Original owner, 185,800K miles