In nashville tuning, your high E and B are tuned as you normally would, but the other 4 strings(E,A,D,G) are tuned an octave higher than normal. The purpose of nashville tuning is basically trying to simulate a 12 string w/ only 6 strings...even when playing the most basic chords you can create some very interesting overtones and harmonic structures. Check it out, it can be a lot of fun and inspire some great song ideas.
If you get a set of 12 string strings and use the appropriate octave's it will work. You'll wind up with some extra strings also. That's what I've done before. Some people call this "high strung tuning" instead of Nashville tuning.
Nashville is replacing 3,4,5 & 6 with the octaves from a 12-string set. (1 octave higher.)
High Strung is that plus you replace the low E with another plain .011 so the 6 string becomes 2 octaves higher than normal. (See David Gilmour on Comfortably Numb. He describes the 2 in a GW article .)
love the sound of nashville tuning. you'd be surprised how many recordings have a nashville tuned guitar in the mix (Stones' "Wild Horses", Floyd's "Wish You Were Here".... i'd love to have a separate acoustic just for Nashville tuning and get it somewhat set up for it....
the guitar should be fine even if you leave it in nashville tuning for a while....
Here's my little trick (if you can call it that): Get a cheap Martin Backpacker guitar for Nashville/High-Strung tuning. (Or a similar, but nicer guitar would be a Vagabond Travel guitar). There's no bass there anyway, so the small body complements the sound of the tuning.