I was wondering was World Showcase restaurants service outside of the park. We would like to visit one, without buying an extra day at the park. Also, how do you reach the restaurants from outside the park?
The only way to do the restaurants in World Showcase is with admission into the park. The only Disney restaurants outside of the park will be at DTD and the resorts. Those are the only ones you can do without needing a ticket.
The kind of thing you're looking for, though, can be easily had in the form of visiting resort hotel restaurants. You don't need to be staying at that hotel to eat there, and there is a TON of variety.
You can get to the Boardwalk-area restaurants (out behind Epcot/World Showcase) by driving to the Boardwalk and parking in the 'general' lot; by taking a bus to the Boardwalk; or by walking/taking a boat from MGM).
But if you have at least four-day passes, the cost for an additional day is under $5.