Hi,
You can get to the 5th station by bus or car, and climb the mountain by yourself from the 5th station to 8th station (the top of the mountain). I have only got to the the 5th station by car. There are lots of people at the 5th station and started climbing to the top. If your stay is not long enough, you better shortcut to the 5th station by bus.
Hope the following site will be of help. JTB is the one of biggest travel agencies in Japan. Many foreing tourist use it.
http://www.jtbgmt.com/sunrisetour/igo/F800.html
Good luck
