Here is a link to the TM, but there really isn't much to it
Link
1) remove battery
2) remove oscillator or continuity block cap (vertical threaded cap in front of the battery compartment)
NOTE: If your scope has a silver oscillator wait several hours after turning it off before touching the oscillator (non-ABC tubes use oscillators) If it has a red/orange plastic block, pull it straight out
3) Unscrew jam-nut that holds the eyepiece on the end of the scope
4) Pull eyepiece assembly straight back, it is a tight fit to the rear of the tube
5) Put your hand over now open rear end of the scope and tilt upwards, tube will fall out (again, if you've had the scope on recently, give it a few hours before doing this, may still be some charge in the tube's circuits).
There are three grub/set screws that retain and fix the focus of the objective lens, you can remove these and unscrew the lens.
Very simple scope. Only the objective lens (and maybe eyepiece?) are nitrogen purged, the body is not (much like the AN/PVS-4).