It's not a hard job, just takes a little time. I think Harvey's boxes are around $350 or so with a core charge added on top of that. I had him do a UPS return ship to get my old box back to him.
You'll need a 1-1/4" socket to get the nut off of the pitman arm. You might soak it for a couple of days prior with some PB Blaster / Kroil / Liquid Wrench. The same goes for the three bolts that hold the box to the frame rail. (remember that if you unbolt the sway bar it will swing down and knock your teeth out so put some blocking under there if you take it loose).
Put your Snap-On puller on and give it some torque. I showered down on mine and it still wasn't moving, so I went for a beer and I heard it hit the shop floor. Sure enough, I took a peek under there and the puller was on the floor and the pitman arm was off! Cool.
Disconnect one of the hydraulic lines from the steering box itself and disconnect the other from the location near the firewall (seemed easier to me). Then re-assemble the one hydraulic line onto the box while it's out of the truck. Have someone help you up top to fish the hyd. line back up.
Button it all back up, put a little thread locker on the pitman arm nut. Follow Harvey's instructions for priming / filling the hydraulics.
Use a regular plumbing monkey wrench to turn the turnbuckle just off the pitman arm to straighten the steering wheel and you're all done.
Time for a frosty malted beverage or five...