xCode 10.3 to 10.4 update, gcc needs removed first? xCode deinstalled?

My company’s pretty far behind the 8 ball somedays so we are just moving to 10.4 now. My computer got upgraded to 10.48 and xCode 2.4.
But
A long time ago I swear I read that installing an upgrade of xCode 2 over a 1.x installation would do bad things to gcc, and it was required to deinstall developer tools first, then upgrade to 10.4 and then reinstall developer tools 2.x. (Or something like that)
Does anyone have a link to this or a definitive reference?

I recompiled one of my xCode apps and ‘upgraded’ it and set it to be a universal app, but it won’t compile now. I get this error:
/usr/bin/ld: warning fat file: /usr/lib/gcc/i686-apple-darwin8/4.0.1/…/…/…/libSystem.dylib does not contain an architecture that matches the specified -arch flag: i386 (file ignored)

It’s also possible that my sys admin did not enable all installed packages when the install of 2.x was installed.

Thanks much,
Chris