As stated above, refinishing is major luthier work. You have to remember the depth of the wood, which is why there is bracing underneath. Glossing will definitely change the sound. Leave it, as is. If, in a few years, if it increases substantially in value, the aging marks will add to it. Take a look at some of the old "bones" and pre-war D-18's. They are pretty worn looking, but sound wonderful and can cost upwards to $160,000. Okay, so the $160,000 one was in mint condition.

As for finish stress, I would be more concerned with the part of your arm that comes in contact with the lower bout of the guitar. Perspiration/sweat can ruin a guitar's finish. There are devices to keep your arm from resting on the guitar. The best device I've seen is to cut off the toe part of a tube sock and pull it over your right elbow (assuming you're right-handed)so it covers that part of your arm that rests on the guitar.