Switch from ULN and update kernel using RHN

One of the test servers is running oracle linux, the /etc/enterprise-release is showing "Enterprise Linux Enterprise Linux AS release 4 (October Update 7)". What are the procedures to switch it to use RHN (I have some update entitlements to spare)? One main task is to upgrade current kernel version "2.6.9-78.0.17.0.1.ELxenU" (which is from oracle) to RHN's corresponding kernel version "2.6.9-78.0.22.0.1" or higher?

There are some posts out there discussing switching from RH Linux to Oracle's. The reverse may be similar but I'd like to get some definitive advises, and where to get the rpm(s) if needed (such as up2date) from RH corresponding to the server version discussed here.