Let's see....
- You'll be putting the truck in neutral, so make sure you take the appropriate precautions when you raise it (wheels blocked, etc).
- If the connectors don't pull off easily, take the hair dryer out and warm them up - the potting sometimes melts in the old style NSBU's and the heat will loosen it enough to get the connectors out.
- Disconnect the shift cable BEFORE you try to loosen the nut on the selector shaft - otherwise you're looking at a broken shift cable. No fun to change.
- Once you have the nut and lever off the shaft, just pull the two bolts that hold the NSBU to the trans and finesse the NSBU off. It's a tight fit around the front driveshaft, but it will come out of there.
- Next, make sure the trans is in neutral (rotate the shaft all the way clockwise for park, then two clicks CCW for neutral. The flats on the shaft should line up with the little diagram cast into the trans).
- The new NSBU will have a small piece of stamped steel on it - that is to hold the switch in neutral. Leave that piece on the switch and install the switch onto the trans.
- Tighten the two bolts to 18-21 lb-ft, remove the stamped steel piece, install the new shield, the shift lever, and the nut.
- Tighten the nut to 15-20 lb-ft, install the cable, plug in the connectors, and you're done!