Hi Mike, welcome to FlyerTalk! Tokyo is an amazing destination and completely worth the trip. It's the first place I went when I started traveling a lot, and I had more than a little bit of hesitation - both from the long time spent on the plane and from worries about language barriers once I arrived in Tokyo. Your post could have been mine, but it turns out I had nothing to fear!
I actually think that longhaul flights are easier for me than short to medium term flights. Especially in business class, the rhythm will be "board, eat a tasty meal, relax with a good book, and then you're almost there"! I find flying Seattle to Tokyo far more relaxing than flying Seattle to Atlanta, actually - more time to chill out! Think of it as an opportunity to catch up on all the movies or books you've been missing out on lately
The other thing that helps is the types of planes that fly long distances tend to be bigger and more spacious, keeping it a pretty comfy ride (
especially in J!)
I also find that for transpacific flights I actually experience less turbulence than small regional flights within the US, since the aircraft are bigger, they fly pretty high up and over fairly calm polar regions. The one exception is that I've noticed the air around Japan does get very lightly bumpy at times for the last hour or so of a flight to Tokyo, but it's completely normal - absolutely nothing to worry about at all.
My first trip to Tokyo started a love affair with Japan that's resulted in me going back at least once a year for the last five years. The country is amazingly friendly, safe, and easy to get around, and I totally recommend a visit - please go and have a fantastic time!
There are also some great resources out there for nervous flyers - do a quick search in this forum and you'll find a great compilation of web sites to check out. One of the pieces of advice in particular that stuck with me was watching the flight attendants - they fly these routes regularly, so if they are calm during turbulence (and I guarantee they will be), you can rest assured everything is fine and normal!
If you want to ask any more questions feel free to post them, I'm happy to keep answering (and I'm sure the rest of the FlyerTalk community will as well).