Hi Louis. I went through a whole world of pain migrating from RH9 to RHES3. Hopefully this post will save you some of that same pain.
The process is basically, for each src RPM, build it (and maybe get an error), then for each built rpm, install it. Repeat this until most of the RPMs are compiled and installed. You'll need RH9 -devel rpms installed (since RHES3 doesn't have the src packages for the -devel rpms that are dependancies of the non -devel src rpms).
Finally, you'll discover that some RHES RPMs simply won't compile from source.
Fortunately, all is not lost.
have gone through this process for you. Fixed the broken src rpms, removed the Red Hat trademarks and have packaged up their own distro.