Good advice so far, but I'll add a little more anyway.
Have a good look at the wiring. If it's the original wiring the old cloth covering is subject to deterioration, causing bare wires and nasty short circuits. You don't need to turn your "New" truck in to a Car-B-Q right away. The only fuse in the system is attached to your head light switch, for the lights only.
Finding the right order of the wires for your regulator isn't too difficult. The regulator should be labeled with a "B", an "F", and an "A". "B" is Battery, and will be coming from the Ammeter. "A" is the larger wire going to the generator. And "F" is the little wire going to the gen. If your wires are like mine, the color codes won't do you much good as they'll all be faded white.
I would probably squirt/spray a little oil into the cylinders to aid with cylinder lubrication. They will probably be a little dry and rusty from sitting. And if the fuel tank cleaning proves troublesome, you could always run a temporary hose from the fuel pump into a gas can to get it running. That'll then provide much motivation to keep going.
As for your trans/fluid drive question... You can probably just change the oils and you'll be fine. The trans uses regular gear lube (GL5 80w90 or similar). The fluid drive uses a HiTrans type oil. I got a 2 gallon jug of Universal Tractor Hydraulic Fluid (ISO VG32 grade) from my local farm supply store (Farm & Fleet). You'll have to remove a pan under the clutch/fluid drive area, then rotate the engine until the drain plug is at the bottom. Pull the plug and let it drain. It'll take a while to drain it all out. Let it sit there over night if you can. Then you'll have to pull out the floor plates and you'll see a round plug at about 1 O'clock on the bell housing. I believe mine says OIL FILL on it. Pop out this plug and you can see the fluid drive. Now rotate the engine until the drain hole lines up with the hole in the housing. You'll need a long nose funnel to refill it. Again it is slow to fill. You'll add fluid until it bubbles out, then wait several minutes and fill again. If you let it sit for an hour and it still won't take oil, it's probably full now. As I recall, mine took over a gallon and a half. Now the trick is getting the plug back in without dropping it. A magnetic socket helps. Or a piece of paper over the head of the plug to make it fit tighter into the socket to hold it.
And while you're changing oils, you might as well to the axle too. And while you're back there be sure to check/clean the axle breather.
And one final piece of advice (for now). Once you get it going, you'll want it to stop. Be sure to give the brake system a thorough inspection.
Merle