You don't need to! JPAN's hacked engine has a feature for that. Download v1.1 of his hack and read through the documentation. There is a section about switching the player, and it has a ton of other useful features, but be careful, the patch erases your rom. Talk to me if you feel like using it!
Thx, seeming as i only have a scripter and a music composer. I would love to learn a bit of ASM so i can change the overworld sprites.. I want to have the main character and have him in his pajamas. and then the screen fades and the overworld sprite has changed to him in his normal clothes. I'm not too smart when it comes to ASM coding..