I hope you have a fair bit of time, it's quite a ways. For starters, google the Frankfurt Int'l airport, and check out transit links they have - I assume there's a bus to Hahn, but I'm not sure there's a train connection. Have only been to Hahn once, and I didn't see a train station nearby, though there may be one in a neighbouring town, and you could get a bus or cab from there. If you can't find a bus link, google "die bahn" to get the German rail schedule, and check trains to Hahn - they might give you a neighbouring town. If all else fails, call Ryanair and ask them how the heck you're supposed to get to the airport.
When you get to Hahn, check out the buildings. It's a defunct US Air Force base, and all the apartment like buildings were once offices and housing. You can still see the planes painted on the sides of buildings, and anyone who has ever lived in base housing (or seen it) will immediately recognize the colour scheme.