Installing MacOS over YDL

[John]

There seem to be lots of howto's about how to have MacOS and YDL exist
together in harmony, but they all assume you have MacOS installed first.  I
have an iMac with just YDL2.2 on it and I would like to add MacOS.  How can
this be done?  I figured I would just install MacOS over YDL and then reload
YDL, but before I can install MacOS I have to do some firmware updates.  Is
there a firmware update program for YDL?  Thanks for any help you can
provide.
John