Thanks to all who responded and for the excellent guidance. It turns
out (after taking it to Pacific Premier for a checkup), that the
problem with upgrading was due to some aftermarket RAM I had that was
hosing up the installer. It's odd that for the 6 years I've had this
G4 with that RAM installed I never had an issue with it, (even
successfully installing Panther and Tiger), and that it would now hang
up with Leopard. So, after removing the RAM, it installed just fine.
But it's good to know that I have the target disk option in the
future. My afternoon upgrade job ended up turning into a 3 day ordeal
but now I'm finished and can start on upgrading the iMac. Happy New
Year to all and thanks again.