As an aside, 2004 is not that old. If the body is sound, it's definitely worth investing some money in maintenance. I'd consider taking it on a road trip occasionally for 50-100 miles. Letting it sit and/or taking only short trips can cause internal problems like rust, corrosion and seizing up.
I concur with basic tune up advice like plugs, fluids, belts, hoses and filters. I think a thorough inspection of the other rubber parts would be money well spent. Replacement is probably not necessary unless there is an obvious problem. If the truck has been in NH all its life, check the undercarriage for rust.
