I agree with both of the above to a certain extent. Whatever you do, don't clean it with bleach or anything. As said, there was no disease, so it'll be fine to just clean it out with plain water.
And as for being attached, I completely know the feeling. Been there, had fish for a really long time and then when they're gone.... it's a terrible loss. At the same time, getting fish again is okay, too. Instead of taking the tank down completely, maybe you should give it a little time and then explore a pet shop for some new fish. Instead of a gold fish, get something different so it's not like you're trying to replace the fish. Treat it like moving someone into a new home. It's part of life, ya know? And while you don't need to do it immediately, it would probably be nice to have some new companions for some time.
