First off, where are you staying? South or north of Nagashima. The closest large city is Nagoya, so you can stay in a business hotel there, and save money. Probably $65 US. In regards to the park, I was just there 10 days ago. The current cost is about $40 US for an all day pass, but remember one thing. The park has shorter hours than traditional US parks. The do open really early though. Right now, they are opening the park at 8:30 am. When I was there, they were closing the park at 5pm, but now school is finally out, so I believe they will keep the park open until 9 or 10pm. Bring a swimsuit. It gets much too warm to not take a break from the weather. The temperature when I was there was 93, and it rained all day to boot. The will not have Steel Dragon open if it rains, but White Cyclone, a really great Intamin woodie will be open. You will just get really wet!
In regards to the crowds, you have nothing to worry about. Even if it is a perfect day, Spaland is a family park, and many people have NO interest in riding Steel Dragon. The wait on the day I was there was 10 minutes. Thats it! It will be 30 minutes at most according to my Japanese friends. You will have a chance to ride it many times. Note, however that you will NOT get the chance to pick your seat. It doesn't work that way in Japan. As far as the ride is concerned...I loved it, but as with anything, try not to get too hyped to ride it. There in NO coaster in the world that can live up to any true enthusiasts expectations. Go and have fun. They have a couple of different rides there including some unique flat rides, and they have a heartline coaster. You don't see those all over! There is a few corkscrew coasters, and also a clone of Montezooma's Revenge. I wish I could go back now....:( Have a great time! Kiotsukide!
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;)Rollercoasters are like parrots...if you take care of them, they should outlive you;)