Just came across this again on another forum ... I posted it up there years ago. Thought it might come in useful for someone on Auszookers at some stage, so here it is. Takes about half an hour per door, doing things neatly.
1) What you're working with... assuming NT/WT Sierras are the same? Mine's a 93 WT. Note where screwdriver is pointing - this screw retains the window frame on this side.
2) Take three of these
3) Insert washers between inside of door and window frame to space frame towards the outer door skin
4) What I used ... $30-$40 from Jaycar for a 4 door kit with master solenoid (5 wire) for driver's door
5) Where the solenoid will be positioned within the door. Insert and check for clearance with window up and window down; also check that the bottom frame that the window sits on will slide past the solenoid as the window is wound up and down.
6) Position of solenoid shown outside door skin. Note position of solenoid drive pointing towards outer edge of door and tucked hard in beneath the door card clip retainer.
7) I trimmed the screw mounts on the non-mounting side to give a bit more clearance to the window. Just use wire cutters.
8 ) Position the solenoid again and drill your first hole. Don't drill all the way through - just make a mark on the paint, move the solenoid out the way, and drill the hole fully. Think I used a 2.5mm drill bit - just fits through mounting hole in solenoid anyway.
9) Insert a bit of steel rod through the first hole to locate the solenoid (the push/pull actuator rod in the kit is perfect, as I used) and drill your second hole.
10) Mounted solenoid at full extension. Bend the door opener rod by hand to make sure it won't interfere with the solenoid or solenoid actuator rod. Check the door handle opens without pulling against the solenoid or interfering with where the actuator rod will go.
11) Cut and bend actuator rod to suit then screw it to the rods. Check lock extends full up and full down before torquing screws up tight. Briefly connect one lead of solenoid to ground and other to 12V to check solenoid actuates - if nothing happens, reverse the polarity of your connections. Flip the polarity a few times, operating the solenoid, to check it does open and close reliably without hitting anything or jamming.
12) Run your wiring. I wind it through the cutouts in the bottom of the door to keep it out the way of the window winder.
13) Solenoid cable + tweeter cable + courtesy light switch for the alarm. Just needs a wrap of electrical tape and some silicone on the grommets and she's done