Too hard? oO Give me a few seconds starting now (2128 GMT+1).
Will download yours, edit the moon to be fully filled and blue.
Edit: Oh my god, I feel bad. 2138 now. Well, I did it twice since I first deleted the .MPQ since I opened yours straight of the .zip, edited it and didn't save it. Whatever.
Download:
Filebeam - Free Fast File Hosting
And: Erasing the edges by painting over them in black wont get a circle out of it. It will have bumps at those corners and will be on a totally black background in the sky. Did you hear of alpha-layers before?