Valve guide seals

Is there any tips to doing this? I am going to replace my brothers and so far I know I need the air hose adapter that goes in spark plug hole. Anything else.

TIA
Doug

You will also need a valve spring compressor.

As you remove each rocker arm and pushrod, be careful that the pushrod doesn't pull the lifter up out of the bore. If that happens, unless you are very good or very lucky you'll have to remove the head to get the lifter back into the bore.

Don't ask how I know this.

You don't need compressed air. Remove the plugs, and put a length of rope through the plug hole. Turn the crank until the piston goes up. The rope will keep the valves closed.

I did that on my '94 without removing the head or using the rope trick although I would not recommend it to anyone except the experienced ones.
You need a valve spring compressor. I used one that bolts to the rocker arm stud (in the case of the 4.0 the rocker arm bolt bolt). I have done this many times in the past on the chevy 350 and 454 that are used in the marine industry.
You do not have to remove the pushrods. However, the piston on the cylinder you are working on must be all the way up. A small soft wire inserted into the spark plug hole is the best way to determine wether or not the piston is all the way up. Those oil return holes in the head should be covered so that the valve retainers not go down there.
If you have experience the rest should be easy. It is a good idea to use the rope if you are in doubt. However, if the piston is all the way up, the clearnce between the valve and the piston is so close that it is impossible for the valve to fall through.
Have fun.