Ooedo Onsen Odaiba, Tokyo

I am a big onsen fan and going to Tokyo in a couple of weeks.
I am planning to go to Ooedo Onsen Monogatari at Odaiba, but am trying to plan this into my very busy schedule, so would like some advice.
1. How long does it take to reach the onsen from Ginza approximately? And I've heard there is a free shuttle to the onsen but can't find out about pick ups etc. Can you help?
2. How much time should I allow to enjoy it? I know this is dependent on personal preference but any advice would be useful. I like to have a good soak, take time to relax and see all the different parts of the onsen. Plus probably have something to eat and drink. I thought maybe 3-4 hours there would be plenty. Any tips?
Thank-you.

How long does it take to reach the onsen from Ginza approximately?

Assuming you start from Ginza Station, the one way trip by Ginza Line and Yurikamome takes about 30 minutes (Telecomcenter is the closest station):
http://www.hyperdia.com/

And I've heard there is a free shuttle to the onsen but can't find out about pick ups etc. Can you help?

Here are the details of the fee buses in Japanese. I can't see one departing from Ginza, and if you are short on time, I think it is better to use trains:
http://www.ooedoonsen.jp/higaeri/access/bus.html

How much time should I allow to enjoy it? I know this is dependent on personal preference but any advice would be useful. I like to have a good soak, take time to relax and see all the different parts of the onsen.

I recommend a minimum of one hour for bathing only (including undressing, payment and everything). A minimum of two hours to also have a meal and enjoy some of the games. 3-4 hours would be plenty.

Thanks very much Uji.