I am new to bike touring and serious cycling, and I'm planning a trip down the Natchez Trace Parkway. I have a mountain bike that I have ridden for years and is in decent condition. Funds are very limited. So my question is....should I just buy slick tires to put on my mountain bike? Or do I really need to be on the lookout for a road bike? There are several decent deals on Craigslist (mostly Schwins--I don't know much about different bikes and which are good). I don't plan on doing much touring after this trip, for a good while, so I would like to do whatever is most economical but also practical for having a successful trip. Thanks!