Diesel fuel is usually OK for that amount of time. Depending on the fuel level you generally have two choices.
One school of thought is to top up the tank with fresh fuel to dilute the old fuel. Another is to run it with the old fuel (and maybe some cetane booster) and get the old fuel out of the system quicker. I tend towards the second approach and, unless there's a lot of crud or water when I check the filter, I'll look to get the old fuel burned off prior to changing the fuel filter.
As long as the fluid levels are up and everything passes the look, feel, smell test, I'd charge the batteries (or be ready to slave it) bleed the fuel line at the fuel filter bleed screw and crank it up.
I wouldn't drive it very far without doing a complete "annual" service.
Be prepared to deal with the usual fluid and filter changes, belts and transmission vacuum lines as needed. I'd run down that list ASAP, but would want to know if it's going to start and run first, so I knew the full extent of what I'm facing.
Assume the brakes will need service. It is more than likely that the drums are pretty rusty. The springs, pivots and parking brake cables could be rusty. I wouldn't touch the parking brake until after checking the rear brakes and cables. You don't want to set the parking brake and have it freeze up due to corrosion.
If the vehicle doesn't have silicone brake fluid, flush it and bleed it soon. Regular brake fluid is very hygroscopic and will likely be contaminated. Heck, flush and bleed it soon anyway.
Depending on what you know about it's maintenance history, I'd consider a preemptive replacement of the glow plugs at an early date. My theory is that for a minimal cost I know that's one less thing that I need to keep wondering about.
When you drive it, you'll likely feel flat spots from the tires taking a "set". Drive it slowly until they go away.
As time and budget permit, get caught up on a chassis lube, bearing and hub lube etc.
There's a good chance that the lubricating compounds and corrosion inhibitors in the coolant are shot. If you don't have a way to check that, or recharge them, flush and refill the cooling system soon.
Don't be surprised if the thermostat has given up the ghost.
Based on how it acts when you crank it up and a good thoughtful inspection, you can set up the timing and sequence of all this.
If you are not already getting commercial pricing at your parts supplier, ask! My experience has been that the local store that's been around forever will usually give you commercial pricing long before the bright shiny chain stores.
Simply explaining to the magager that you are a collector, commiting do your business with them and asking for a discount will go a long way to keeping the hobby more affordable.
Good luck
Lance
