With the transmission fluid that neglected, you need to clean the '
strainer' (wire mesh screen) inside there. It's behind a triangular plate on the lower front face of the transmission. Opening this will dump the transmission fluid, 4+ gallons. Some of us have had to scrub and rinse with diesel (poured in from the dipstick hole on top) to get crud out of the filter cavity.
Often that strainer needs to be replaced. So don't open the cover until you have lined up the strainer, cover gasket, and probably the o-ring that seals on a shoulder near the end of the screen mesh.
Hoyetractor in Texas is where I got mine.
Fredricks in Alabama might be faster for you. About $50-60. Hey
Danny, do you stock these strainers?
Everything else is common local stuff.
I would just play around with the tractor for a couple of days before buying the service stuff. I would start service by re- torquing everything as soon as you have manuals and specifications. You will probably discover some small items that can be added onto a parts order. Maybe a proper overflow bottle?

You might need to order the fuel filter and its o-ring if that isn't available local but there's no hurry.
Two instrument panel bulbs should light before starting. The overheat light can be tested by sliding up the boot at the temp sensor (top/front of the block) and slipping a grounded wire in there with ignition on. This should light the third lamp.
Thanks for the photos!