Yeah, I tried to get the packages from yum with that exact command, but it's looking for an 'x64' set of packages. I'm at work right now so I can't get the exact error, but I recall that it's looking for an 'x64' package directory. It errors out saying 'file not found' or something similar. There's no 64-bit packages on that server. I checked.
I've been able to get 64-bit binaries for everything else (NTFS driver, nVidia driver, etc.) but I can't find anything that will work for this.
< edit>I think I just found the solution:
this review of FC3-x64 said that they were able to get XMMS working with MP3s by downgrading to the 32-bit version of XMMS....I wasn't aware that you could even run 32bit apps in FC3-x64. Sw33t!
I'll post my results when I get a chance to try it out later. < /edit>