So, I solved my own problem. I thought I'd share, in case any other mac-users find their way to this mod. The problem was that the file was an .exe (which stuffit expander can't handle) which I have learned can be rectified with a program like filejuicer which seeks out any goodies hidden away inside the .exe. Afterwards you are left with a .rar file (which stuffit expander also cannot handle). However, if you use a program like MacPAR_deLuxe you will be left with the mod, just as was intended.