You can flush the diesel pump with regular gas using the hand pump, that can free up fuel elements that got stuck. Leave the gas in the pump for a while, and afterwards flush with fresh diesel until the fresh diesel comes out of the return line.
The diesel pump has it own oil supply, so that needs new oil too (as does the engine).
The air filter is probably a oil-sump version, so replace the oil in the air filter too.
The spring inside the governor of the diesel pump has been compressed for a long time, that can cause performance issues. Replace if necessary.
The injectors are in a unknown condition and have not seen any action for decades. You might want to consider rebuilding them.
The membrane of the diesel pump governor might have dried out and may be leaking air, that will cause a high idle or a runaway diesel. Under normal conditions it would get sprayed with oil/diesel, keeping it wet and air tight.
New main diesel filter and new prefilter, but you probably know that.
Engine oil filter consists of two parts: a re-usable main filter that looks like two discs on top of each other. The dirt is on the outside. Be careful not to get dirt inside.
Underneath is a bypass filter, which can be replaced.
If you start it for the first time, stand ready with something that can be put before the air intake (a plank of wood for instance), so that you can kill the engine in an emergency, although pushing in the start/stop knob should normally do the trick.
If the handpump doesn't work anymore, it can be replaced.
Engine is between the seats:
and you need to remove the front to turn the engine: