http://www.parktool.com/repair_help/FAQindex.shtml and http://www.sheldonbrown.com/articles.html will tell ypu how. Change the cassette to a 13/30. You may need a new chain to get a few more links, a SRAM or Wipperman with a replacable master link is a lot easier to deal with than the Shimano chain. 25 mm tires will be more comfortable for riding these distances, but the current ones will do while you are training. Shimano A520 pedals are great for touring as they have a platform to provide extra suppotrt for the foot, and they can be worn with SPD shoes which you can walk in. Ask you grandfather what he thinks of these suggestions.