I am trying to compile stepmania and maybe even frets on fire for my PS3 which is running Ubuntu. I especially want Stepmania though as my mom plans on using it for exercise and I haven't exactly gotten her a Mother's Day gift yet. Anyways, I just want stepmania to work on Ubuntu 7.04 for PS3 so if someone could help me out with that then it would be fantastic.
Also, is there a good chance that I could compile most programs for PPC or would I have to make some major changes to the code in order to get some programs running on PPC?
I can't find how or where to run GCC.

You have to use a PPC compiler. Download the PPC version of gcc.