Space World only offers an all-day free pass, unlike many of the other Japanese parks which offer free passes and admission-only tickets. Food options are pretty standard. The park has a kyushu-style ramen which was pretty good and since it's a local specialty you should give it a try - I found it in a restaurant across from that tunnel coaster on the Venus side of the park.
It's really easy to get to Space World - just ride the JR train to Space World Station, and then it's just a very short walk to the park. It takes about 10-15 minutes by train if I remember correctly. If you go on a good day when crowds are light, you can visit all the attractions in about half a day, but there's enough to do and the park is fun enough to spend an entire day.