I just did this last week. My engine has 371,493 miles on it and the guides were in spec. So were the valves; they only needed a light grind to clean up. The head, however, was not. The shop had to cut 0.015-in off the bottom to flatten it. Head bolts were also another matter. I had to replace (6). Well, not had to, but chose to. They were all above the minimum, and actually only a few thousandths below the new lower limit, but since they were in the middle, where the hump was, I didn't feel good about them. The one in the rear on the exhaust corner was also toast.
I also would not order the shims. The machine shop can compensate by trimming the valve stems. Much cheaper.
You should replace the heater tee, if you are replacing all the other heater components.
If your PS pump bearing isn't squealing, it's probably still OK. The pressure hose is something to look at, though. If it's at all suspect, you'll never have a better time to get at it to R & R.
I spent several hours degreasing the engine before I opened it up. That was time well spent.
Remember to pin the fuel supply line so the open end is above the level of the tank; if not it will siphon fuel onto the ground under the truck until the tank is empty.
Lastly, check the sensors, and connectors on all the sensors, on the intake side of the head. Three of four of mine crumbled in my hand when I tried to pull the harness. I was able to save two of the harness side connectors, but the engine temperature gauge sensor connector (the one closest to the front) literally came apart in pieces too small to recognize as a connector. You can still get connector housings, if you loose one, and all the sensors area available as aftermarket; I chose to replace the ECU temp sensor with OEM, but the others I cheaped out on.
Oh, and do clean the engine side firewall very well, before you pull the harness through.