First thing you should know is RHL9 has not been supported by Red Hat for over two years and support from Fedora legacy will end this year also, so basically it is a dead OS.
Since your hava book for RHL9 may I suggest staying in the Red Hat family download/install something like FC5 or CentOS (try the x86_64 bit version since you have a 64-bit CPU);
Fedora Core support is around 18-24 months while CentOS support life is the same as RHEL4 (Currently to Feb 29, 2008 and Maintenance updates to Feb 29, 2012).
While it is possible to download/build/install a 2.6 kernel in RHL9 it is a lot of extra work and time that would be better spent installing and using a modern supported OS.
No you cannot install a 2.6 kernel then install RHL9, it does not work that way. Some old sites as per your request;
A place (for example only) to get either the FC5 or CentOS media if you do not own a burner or have a high speed connection;