The problem with my truck is apparently just a bad battery. The passenger-side battery has a manufacture date of 11/04, but the driver-side battery appears to be the original Motorcraft battery that came with the truck in '96. Price Autoplex only sells Interstate batteries, and the one for my truck was $100, so I just paid them the $30 diagnostic charge and I'll take care of the battery myself. I've bought two Wal-Mart batteries in the past, and haven't had any problems with them, and that's what I plan on buying this time.
Update @ 8:54pm: I thought I'd update this post rather than create a new one. I just got done replacing the battery, cost me $60 for a new EverStart Maxx. For some reason, there's this nagging doubt in my mind that it'll fix the problem. I'm taking bets on how long it'll take before the truck dies again and leaves me stranded somewhere. I'm guessing it'll be sometime next Thursday, when I'm supposed to leave for our camping trip in the Swell.