Osaka to Lake Yamanaka and then to Shinjuku

Hi, we are planning a one night stay in Lake Yamanaka on our way to Tokyo.
First, what is the best way to get to Lake Yamanako from Osaka? We are not interested in trekking as we will have our luggagewith us.
Next, where can we stay to enjoy the scenery? Not interested in Onsen but a regular resort
Is one night enough to do major sightseeing?
Lastly how do we get to Shinjuku from there? Thanks.

First, what is the best way to get to Lake Yamanako from Osaka?

Take the shinkansen to Mishima and then the bus to Yamanakako. If you have the Japan Rail Pass, it is slightly cheaper (and can be faster) to take trains from Mishima to Gotemba and then catch the bus from Gotemba, instead. More details are here:
http://www.japan-guide.com/e/e6905.html?aFROM=2157_6900

Next, where can we stay to enjoy the scenery?

I have no specific recommendation. But this website lists resort hotels:
http://www.japanican.com/

Is one night enough to do major sightseeing?

Yes, I think so.

Lastly how do we get to Shinjuku from there?

There are direct buses:
http://transportation.fujikyu.co.jp/english/gettinghere/01.html
http://www.japan-guide.com/e/e6905.html

Thank you Uji san.