I am so hoping to visit the snow monkeys when we are in Tokyo. I am thinking that we will take the train to Nagano, then find a tour to the park for the afternoon or day. Has anyone done this before? Can you recommend a tour? We are also looking for a hotel in Nagano, for 1-2 nights, that is about $250-300 per night if possible. Maybe a ryokan would be great!!! Thank you!

I have not done this but to plan such a trip I would:

1) read this:: Jigokudani Monkey Park (Snow Monkeys) - Yamanouchi Travel
and take note of the walking involved. Would want to stay in a Yudanaka or Shibu Onsen ryokan. There are sponsored links for lodging but below that are links to "Top Rated in Yamanouchi".

2) go to agoda.com to find/book lodging. Your lodging budget is quite healthy for Nagano city and should do well for the two onsen towns.

3) for a tour, I would start at klook.com and enter "snow monkey" in the search box. See that there are tours from Tokyo as well as Nagano. (yes, you do want to see Zenkoji in Nagano city). Private (expensive) tours are also available.

4) take any Hokuriku Shinkansen train to Nagano, with slight preference for a Kagayaki train, expecting reserved seats to be available at the
last minute but probably book a few days in advance. I would consider trying Gran Class seats.