[CentOS] How to upgrade WBEL4 to CentOS4?

Hi,

I've got a couple of servers that are running WBEL4 that I would like to 
upgrade to CentOS4.  I noticed that there is a FAQ which explains how to 
upgrade WBEL3 to CentOS3, but haven't found anything similar for WBEL4.

Are the instructions for the WBEL3 upgrade the same for WBEL4?  Should I be 
doing something else instead?

Any help would be greatly appreciated.

Thanks,

Eric