Hey, people. I need your help. I ride a 1987, entry level Panasonic road bike (DX 10000). It's a 12 speed (2 in front, 6 in rear) with 52 & 40 teeth on the front chain rings and 13-26 in the rear. The crank also measures out at 190 mm. I'm trying to figure out whether to upgrade my drive train or just to invest in a new touring bike. I can possibly afford Jamis or Surly entry levels, although it will be tight. Nothing on the Panasonic is particularly nice, but it has a steel frame and works well enough.
I want to do a tour of NC this summer--approximately 650 miles from mountains to coast. I've done a similar tour in Belgium on a MTB before, but not on my current bike. While my bike is well-suited for daily city commuting (I carry heavy grocery loads home on this bike) and weekend joy rides (40-50 miles), I was told the gear ratios wouldn't be up for touring. I plan on traveling very light (camping, but not necessarily cooking), although I have some heavier-duty Arkel panniers in case I decide to bring more along. I'm estimating a week of riding. I'm also young and fairly fit, so I don't know if I'll need extremely low gears (perhaps I'm overestimating my endurance, however).
Any help, suggestions, advice, or resources would be greatly appreciated. I'm relatively new to cycling, but certainly hooked.