Oh, I thought you just had to replace the pac that the download gave me. There were no instructions so I'd just assumed. It's called "Sacred Updated Hero of Termina" and it's by kien. I'm pretty sure it uses a Majora's Mask inspired moveset for him.
I'm having another problem though. I was replacing costumes, and now my game goes to a never ending black screen right after the Project M screen that comes up after you hit play on the launcher. I'm not sure what could be wrong. All the costumes and pictures I downloaded before worked fine, and then I downloaded "Kapedani's PM 3.6 Build" and just imported some of the costumes and battle pictures that he used onto mine, and suddenly the game doesn't work anymore. I know the models aren't the problem, because I replaced the fighter folder with a clean backup and it still didn't work, so I'm thinking it has something to do with the pictures, but I don't know what. They work on Kapedani's build, so I don't know why they wouldn't work on mine, and all the pictures are the right size. Any suggestions?
Edit: The Young Link mod doesn't have a PSA for PM. It only has VBrawl and Minus. Would VBrawl work with PM?
Edit 2: I've narrowed the problem down to the stock icons. The stock icons are what is causing my game to have a black screen right after the PM logo on launch. I'm using costume manager and putting in 32 by 32 pictures for stock icons. Stock icons have worked up until I started using the ones from Kapedani's pack, but I don't know why the problem would be specific to those ones, since they are all 32 by 32.