Im too scared to play it now without mods (i definitely will soon though). Any help on how to mod?

The game's files are open; you can open any image file you want, edit it, then save it and it'll work in game.

You can replace sounds by deleting the file, and renaming a different file in its place.

You can edit the code of the game by downloading the latest version of Blitz3D and getting the source on GitHub.