I need advice on storing a vehicle for long periods of time. Heres the car. 1984 300D - Imgur

I'll be leaving for active duty USAF in a few months and refuse to sell my TD Benz. The 78 Non Turbo and the Civic I'll be more than likely selling.

We have a two-bay garage and my neighbors have a barn, both of which are visible in the photos. I doubt my dad is going to give up a bay for a car he doesn't have any interest in and the old barn isn't really ideal because of mice, lack of good weather and temperature protection.

The basics of storing a car I've got down

• Clean it, Wax it, Cover it
• Fresh fluids, oil, washer, brakes
• Top off the diesel tank
• Parking brake off
• Battery disconnect switch
• I won't raise it off the tires, my dad agreed to drive it for an hour or so by-weekly

Have any advice? I'd totally be willing to spend $1600-2000 into the investment of building car size shed myself. Having my own workspace would actually be great, I'm 23 and my dad hates when I change my own oil, he about lost it when I changed a cylinder head... lol sigh. I keep a clean workspace, he just doesn't understand cars. Anyway, If the barn shows itself to be a good option, is there a way to isolate it from the rodents/moisture?