There are guides for compiling GCC at http://linuxhelp.150m.com and http://linux.50webs.org/ under the title:
"Free Compilers and Cross-Compilers for Linux and Windows."
GCC version 4.2.3 is covered in:
GCC version 4.3.0 is covered in:
You can also discuss the articles here:
GCC version 4.3.1 still has some of the same bugs as 4.3.0,... guess I should have written a few bug reports.