Good start to get me on the road... There is a good chance I have misplaced the key, can (or how should) it be hot wired, or does the switch need to be replaced? Does it have a regular or glow plug(s)? If glow plug(s) is there a spot on the switch sequence that needs to be "activated", for example like an old time choke?
I remember hearing that diesel fuel will grow "algae". I forget if it got thick or clogged lines or something else. By draining the diesel do you mean just the fuel in the lines and fuel filter, or also drain the tank? We also had Yanmars (both 2 and 3 cylinders) that used old peanut oil. It was wonderful to smell the fumes, but I vaguely remember they had to be started with something else and then switched to the peanut oil. I only mention this to try to get straight in my mind how to deal with one tractor at a time.
Don't assume or give me more credit than I deserved...I really know nothing about diesels. Tractors are located two hours away so am trying to gather as much information as I can ahead of time. Thanks again.