First thing you'll need to do is discharge your extinguisher if it's full. The gauge on the side should tell you what the status is. Don't try to disassemble the tank with pressure inside!!

To begin the disassembly use channel-lock pliers or some other tool to loosen the hex cap nut on that holds the valve to the tank. Pull out the suction tube and the valve assembly. You'll see the magenta arrow is pointing at the threads where the valve was secured to the tank.

In the above pictures you can see the finished product. While it may not look pretty it is VERY functional and I'm considering getting another one to add to it to get a total of 5gal capacity. The best part of this setup is that I can leave the tank at home when I don't need it. It's not permanently mounted in the Jeep.

Below is a description of what the arrows are pointing at:

cyan - a tank pressure gauge. I drilled out and used a 1/8" NPT tap where the original plunger came up through the valve body to contact the squeeze handle. As and extinguisher this is a none threaded hole that the plunger pin diverts the water out of the discharge hose. With the pin removed this hole has to be plugged for the tank to hold air.

white - is a 1/8"NPT plug that I used to replace the extinguisher gauge. It's not useful for accurate pressure readings. There is only a very small hole to this port in the valve body so it wouldn't use useful for quantity air flow. I could have put the gauge here instead of on top but I like it on top better. (Easier to read)

purple - this is where the original discharge hose was and I cut it off, and hose clamped in a brass barbed fitting then used a T fitting and to get to my input/output to the tank.

red - this is a female quick disconnect that connects to the coil hose which then connects to my pump setup. This allows for the portability of the tank.

green - this is a small regulator that I could use if I were running air tools. At the moment I don't have any air tools so I run it wide open when filling my tires.

blue - this is a second female quick disconnect that connects to my bulk hose that I use to put air in the tires. I bought a 50' hose at Home Depot and then built and clip on air chuck/hose piece so that I don't have to hold the hose on the tire valve stem. Having a female disconnect on both the input and the output allows me to fill up the tank and then disconnect it from the system and have it still hold air. A Male disconnect anywhere in the tank setup and the tank would empty right away.

That's all there is to it. All of the fittings and quick disconnects etc. I purchased at Home Depot between the plumbing section and the tool section. 2.5 gal isn't enough to fill one 33" tire back up after airing down but it is a big help. Having a tank allows the compressor to shut off every once in a while so that it's not running the entire time I'm trying to fill 4 tires.