After completing the first round of a Hold 'Em tournament, do not go "all in" on a hand in the later rounds. When you get down to about $500 or more, when asked if you want to play again at the end of a hand, say "No." You can restart the tournament on the round you are currently on instead of completing the earlier rounds again.
Go next to the tournament table in the Wild Corral casino. Use the map to find the northeast corner of the room and look at the floor. You will find a red poker chip that allows you to enter the Nebula. Additionally, enter the Air Hockey room from the right side entryway. Look along the floor of the right wall to find a red poker chip. Pick it up and enter the Nebula.