What year is that one? I have a 1960 I picked up at an auction a year ago for $700. I've seen them advertised with prices all over the map. Having the factory loader adds quite a bit of value.
The link below has most of the manuals. The hydraulics system manual link doesn't work.
Here's the answer to some of your questions:
King pins: Never done them, don't look like they'd be particularly difficult.
1: Hydraulic bypass valve. Open for normal operation, closed to provide pressure for external hydraulic equipment.
2 & 3: Valve covers. The holes are for pins on a spanner to remove them.
4: Fuse holder, yours is missing the top part. Takes a 3AG style fuse.
5: Light switch, lights probably won't work without the fuse.
6: Glow plug indicator. This engine uses four glow plugs wired in series (two contacts on the top of each plug), which are then wired through the glow plug indicator, which glows orange behind the cover when the plugs are hot. Don't bypass the indicator, you'll fry the glow plugs instantly.
7: Wiring for the taillight, I believe. The lights on mine are long gone.
8: You won't feel any resistance when moving the PTO lever. Forward is disengaged, back is engaged. Put it in the engaged position & see if you can turn the PTO shaft. These tractors also have a two stage clutch...pushing down until resistance is felt disengages the drive clutch, pushing down further disengages the PTO clutch. If it doesn't work, try adjusting the pedal first.
9: Adjusts the brake pedal free play. Will engage the brakes with less pedal motion, but can't make up for badly worn bands.
10: I fill mine to a little ways below the top of the tank. If you fill it too full it'll overflow when the fluid gets hot. There's a filter on the supply line to the pump where it comes out of the hydraulic reservoir which tends to get clogged. Remove the bracket holding the lift valve lever, and pull the supply line straight out to remove the filter.
11: Got me...I haven't figured those out either, although I really haven't tried.
12: There should be a plug on the side of the transmission case, don't remember where off the top of my head. Remove the plug and fill it until the oil runs out of this opening.
Watch e-bay for paper manuals. The pop up occasionally. Binderbooks should also have a manual.
Wish I had one of those loaders. It's a pretty handy size tractor.