Hi Handi,
I've not done it but I imagine it can be done. I do know that changing the light bulbs in the warning light cluster is not so easy. Mostly due to the confined space. And on my tractor, the bulb in the gauge cluster was not the bulb MF sold me, so I ended up at NAPA. I changed every one of them while I was in there.
I recommend you do some searching on fuel gauges and see what you can find that's simple. But I think you'd probably have to replace the float assembly and install the gauge to work with it. Finding a float assembly that would fit your tank or modifying one to work might be the biggest challenge. I'd pull out the one I have and take it with me to the store.
Another good site to learn from is the Chinese Tractor Owner's Association on the web. I think most of their tractors have gauges, so it may not offer any learnings in this instance. But I've picked up a lot of tips from reading posts there.
If it were me, I'd just count on refueling the minute the idiot light came on. You could buy a fuel bottle at a camping store, keep it full of diesel and store it somewhere on the tractor as a reserve supply. I take one to the woods filled with premix for my chain saws. They hold about a quart and they are made for fuel, so I think it would work.
Did you ever get the correct owner's manual? I've never figured out a way to make my scanner scan all the pages into one file, or I'd send a copy to you!
Let us know if you do the mods!