I just did this on a 2014 S King cab, and learned a few things about the power window conversion:
1) Your manual regulators must work EFFORTLESSLY. I could raise/lower both sides with one finger before I installed the kit.
2) Even then, the motors in the conversion kit may be too weak. My right motor lasted 1 day before it wouldn't raise the glass. The left lasted 2 weeks.
3) I wound up replacing both sides with OEM style motor/regulator combinations (repair parts). I found the motor/regulator combos (at different times) on Amazon. Keep an eye out for "warehouse deals". I got a Dorman 741-349 for $15 (right side), and a Hansun 8832-0733 (left) for $25. The Hansun is faster and quieter. The Dorman has a lifetime warranty. Both perform well. Both installed with no special modifications. Amazon also has at least 2 listings for pairs (both sides) for less than $60. You can find these by searching Amazon for the Dorman or Hansun part number.
4) Amazon also has several listings for "Universal Power Window Wiring Harness" for about $25. Factory power windows are on a 10a fuse, and these kits come with a 30a. You'll have more than enough juice.
5) I had to modify the universal harnesses to wire the motors. You can either see your local Self-serve junkyard and cut a couple of pigtails from a Nissan (2-wire from either side, front or back), or see your local parts store to see if they have something. You'll need to splice these in.
6) I wound up carefully re-bending the plug connectors on the universal harness to obtain a very firm grip on the pins at the motor (no mods to the motors, so warranty on them is intact). I used the neoprene sleeves from the universal harness to prevent shorting the wires in the motor's connector. A dab of RTV would probably also work. If you make a mistake doing this, there's always option 5 above...
7) If your motor turns the wrong way, you can either swap wires on the motor, OR turn the connector on the switch 180 degrees.
8) The filler plugs in the universal conversion kit require you to enlarge the holes for the window cranks. The existing holes are 1-3/8" (or 1.375" or 35mm). I found chrome 1-3/8" hole plugs at Lowes for $1.54 each. These coordinate with the door handles as-is, or can be painted. They look as good as the 'kit' ones pictured above, maybe a bit cleaner.
9) If I had it to do over, I'd use a pair of filler plugs from Lowes ($3.50), a universal wiring harness from Amazon ($25), and a pair of motor/regulators from Amazon ($60). Total less than $90 (plus pigtails if you want to use them). It's a lot less work to swap regulators than fighting to get the universal motors mounted. Fishing all the wires is the biggest pain in the butt.