Advance booking - Tateyama alpine ticket

We are travelling in a group of 12 person to Tateyama alpine route in April 2008. Want to do some early planning. We would like to make advance booking sometime early next year for the through ticket from Toyama to Shinano-Omachi. Can anyone who have done this route advised
1) how and where we can get this ticket, preferably in Tokyo area.
2) we are planning to stay overnight at Murodo. Can this through ticket be used over 2 days.

. . . this trip around 7 years ago. If you are in Japan you can get the advance pass at JTB. They also provided me with a map. JTB offices (particularly in Tokyo) usually have someone who speaks English.

I went during peak fall season and it was insane. Never again. Had to wait two hours for the next boat tour at Kurobe Dam. I figured might as well wait because I'm not coming out here again. But autumn leaves were fantastic.

Early May should be a good time as snow will still be on the mountain and green leaves will emerge.

The ticket can be bought in advance, but it will not secure you any reserved seats (there are none). If it is crowded, crowd control is handled by first-come-first-serve tickets (seriken).

Thank u Uji. Yes, we realise that the through ticket only saves us the time to buy ticket at each point. Still need to get boarding number and queue to board.
We planning to stay 1 night at Murodo.
Can the through be used over 2 days?

Can the through be used over 2 days?

Yes, I am pretty sure.