Hi again
Unfortunately i've not been able to find any park hours listed more than 6 months in advance. However, I believe that the hour for the parks stay fairly similar each month from year to year. The opening hours for last March/April are show on the touring/crowd calendar website i mention in my pre-trip report
http://www15.plala.or.jp/gcap/disney/
You'll need to translate the page to English - then you can select the month you interested in by pressing the Prev Mon button near the calendar and the Month heading...if you hover over any given date or click on any date it will give you the opening hours at the top of the box (just under the date heading)...it appears that in March of this year hours at Disneyland were generally either 8am - 10pm or 9am - 10pm depending on the date - I also saw the occasional 8:30am opening. It does also appear the quieter the day the later the park opens. Opening times were very similar for Disney Seas though I saw a lot more 8:30 opens. Based on that I reckon you can be pretty much guarenteed the parks will open between 8-9 am and close at 10 every evening (I have noticed that their isn't a lot of variance with Tokyo Disney Resorts hours)...
I reckon your smart to miss the things that you've already ridden in the US - Toy Story Mania looks visually impressive in Tokyo, but the ride is, from what i've read, basically the same. Same with things like Star Tours...I've seen videos of Splash Mountain and that is a little different and worth a look I reckon, I'm not sure about Space Mountain or Big Thunder Mountain though I have heard there are better versions of both those rides in other parks (namely Disneyland and Disneyland Paris)...Pooh's Hunny Hunt looks like a hit to me and Monsters Inc Ride and Go seek looks ok, and is different.
With Disney Seas rides my priority is Journey to the Centre of the Earth since i've heard it's AMAZING, Indiana Jones, since I love the Disneyland version and this one is supposed to be much more intricately themed - though the ride is basically the same. I also want to see the shows, Fantasmic, Legends of Mythica and the Little Mermaid show in the Mermaid Lagoon area of the park...Just a note too, the Tower of Terror ride, while a similar ride system to Paris and Anaheim versions, has a completely different story and amazing pre-show and queue so if you get time it might be worth a look...Also i've heard 20,000 Leagues under the sea is a great dark ride with some cool effects.
Getting so excited for my visit now
Hope this info has been helpful