This really isn't a CUCV specific question, but since the old fuel is in an M1009, this is as good a place as any to ask. A google search revealed that diesel can degrade and grow algae, both of which can degrade and cause problems.
My question is this, is there a product that can be added to the diesel which will restore it or does it need to be drained and disposed of?
How long was the fuel sitting?
If it hasn't been sitting for too long, I would:
*I would iff possible, wait for a very hot, dry day and let it sit for several hours in baking heat. This is what the home-brew bio diesel makers do to their own personal vehicles to help evaporate water.
*I would also change the fuel filter
if possible to do w/o priming. And use seafoam to prime the fuel filter. It know it's possible on other diesels, but I'm not sure on 6.2's.
*Go crazy with the white bottles of Power Service or whatever it is. It's got a diesel fuel base, so you can pretty much fill your tank w/ the stuff. I'd also add a few bottle of seafoam to the tank as well. And even a bottle of Stanadyne. Make a cocktail!
This is just what I'd do if I knew the fuel old but not so old I felt it was half varnish and sludge.