Nagano for one day

Travelling from Tokyo to Nagano, am intending to stop at Matsomoto castle on route, how long should I allow for this and are there luggage lockers at the railway station?
Also there seems to be some incredible sights around Nagano, bearing in mind we only stay in Nagano for one night before moving onto Kanazawa what would everyone's top recommendations for things to see/do be? Yamanouchi, Kamikochi (would love to walk there but looks like a complete day?) ?
Never enough time to do everything!!
Thanks

Hello, I remember I used a coin locker at Matsumoto station when I visit Matsumoto.

There are a city tour bus in Matsumoto city.

http://welcome.city.matsumoto.nagano.jp/

Kamikochi is beautiful place to walk around, but the weather always changes, so you should prepare for rain.

I often go to Azumino city. It is also good place to visit.
You can get there by train, and there are several bicycle rental shop near the station.

http://www.azumino-e-tabi.net/en/

Thanks for the reply, the bus tour sounds like a great idea...how long is reasonable to dedicate to Matsumoto castle....what about Nagano , what would your recommendation be for such a brief visit ?