I would drain the fuel and replace with fresh fuel. I doubt anything 5 years old will be any good.
Also check all rubber hoses, lines, especially fuel lines for cracks. Replace anything cracked or dried out. If you're draining the tank, now's the time to replace the fuel lines. If they're 20 years old they're well past due.
Also check the brake hoses, and make sure the brakes aren't frozen. Again I'd flush the old fluid, it's overdue.
Personally I'd also crank the engine by hand to make sure it's not frozen. If you met resistance try some oil in the cylinders.
A fresh battery, fresh gas and plugs will go a long way towards a successful first start.