My mario rom is ruined!! What do i do?

[floppingcheepcheep]

Smb1. Also why is this gonna matter?

the reason why is because every ROM for every game contains different types of data. anyways, if you want to modify SMB1, you can modify the code using ASM patches (if there's any), or to modify the graphics, you just have to go bellow the game data. and by the way, i don't think i would recommend tile layer pro, for easier graphics editing i would use YY-CHR (latest version here).