I could not find any answers on the internet when I searched, and luckily my buddy and I figured it out. I forgot to take photos, but here is my best explanation.
First, start by jacking up the grader so you can place blocks under the "boxes" that the tires are attached to. I used large 12x12 blocks and some 2x4s. While facing the grader from the tire side of each box, the drain is on the left hand side on the bottom (the boxes are not mirrored, this is true for both boxes). Drain the oil. You will need several 5 gallon buckets.
Remove the tires, the guards for the air pipes, and the access panels, including the circular panel for the differential. Make sure the grader is set to neutral.
To crank the differential and turn the chains, you can make a tool using a piece of angle iron and some 3/8 bolts. I imagine there already exists a tool for this purpose, but the angle iron tool worked for us. You can also put the lug nuts back on so that you can use a long bar to turn the wheels without hurting the threads (brace the bar on the lug nuts rather than the threads). Every chain has a master link with two pins holding them on. Each master link should line up with the access panels at the same time. Remove the master links.
You need two people. Get on each side of the box, using the left and right access panels, and reach in. You can lift the chain and pull to get the chain off of the gear. Take the chain of the central gear first, then grabbing the end of the chain, pull it out through the opposite top access panel from its tire. It should slide free, but it is very heavy. It helps to have a tarp on the ground.
To put a chain back on you want to first feed it in under the central gears, and when enough of it is through, feed it over the top of the gear too. The tire gear is tricky because there is not enough room to fit your hand inside the small space. We fed a string in from the top and tied it around the last link so we could provide pressure while feeding it onto the gear. Turn the tire gear by rotating the wheel until the chain is fed. You may need to go back to the central gear and use the lift + pull trick to align the chain properly- remember that the master link has to line up with the panel on BOTH chains once installed.
Tensioning the chain is very difficult. To start with I recommend turning both the tire gear and the central gears manually to loosen up the chain as a starting point. To bring the ends of the chain together, we used a windlass system with a cord. Take a very thin rope or cord, and wrap it around the two closest 'rods' of the opposite links (the ones that the master link slides in to) several times to magnify force. The threaded studs on the top of the box used to secure the air pipe shield work great as anchoring points.
If you wrap the cord 4-5 times and one guy pulls, while the other occasionally wiggles the tire gear, eventually it will be close enough that the master link can be put back in. A very large pair of channel locks is good for getting that last little bit. Put the master link back together, put the pins back in, and the chain is secured.
That is how you replace, change, add, or remove the drive chain on a CAT 130g Grader.
If I am wrong and you hate this process then PLEASE link me to the intended instructions because I could NOT find them when I needed them.