Ok for those who were wondering how he survives on the moon without heat (also air) the cut scene at the start of this level explains it, now the first enemy you see is the most basic one, he floats up and down.
Continue right and a space ship appears, climb up the ladder and here you'll encounter your next enemy, these guys just walk back and forward and do almost nothing.
Continue straight up the ladder as there's nothing of particular interest to the left or the right, there's a beam stopping you from going up again so continue to the right.
Here's the first treasure but it's stuck behind this beam, we'll have to come back for this.
Follow the path around until you reach this switch, this'll release Fenton.
Now the gravity is turned off and you have to float around so you can turn it back on using the switches, after completing this continue to the left and up the ladder.
Follow the path to the left and up and you'll reach the first piece of the Gizmoduck suit, after collecting it head back down and all the way to the right.
When you reach this point, head up the ladder for 3 screens.
Now you have to go across a series of floating platforms and enemies to reach the 2nd piece.
Head all the way back down here and the beam blocking the piece is gone so you're free to pick it up.
Now head back out of the ship and back to the crash at the left of the screen.
Now you have Gizmoduck to help you out with any enemies or blockades, speaking of blockades head all the way to the right to find just such a blockade you need cleared.
Here's that blockade and it's gone.
Head down 3 screens until you reach this point, now jump over this wall to get the final heart upgrade, after collecting it continue down to reach the boss fight.
There's the Green Cheese of Longevity! But a rat reaches it before you do and becomes a monster.
He has 2 attacks really, first he runs and jumps to try and hit you, and you can hurt him while he's like this.
After you hit him he glows green and is able to dash and teleport around, avoid this and soon enough he becomes normal again and able to be damaged.
Now with the rat dead you can collect your green cheese of longevity.