glad you got it to work...
"c" is correct for boot from optical drive, but it's "command(apple)-OPTION-o-f" to get to the openfirmware CLI. The rest of what I said is ture. Some "old-world" power macs with ATI video and a APPL-ROM (as opposed to ROM-in-RAM that new machines use) may not initialize the display when booted into openfirmware. The default interface for these is through a direct-terminal connection to the modem port (not the printer port). Video can be initialized from the serial port interface, or you can try a blind initialziation. Do a google search for the strings needed. They are different depending on the graphics chip used.
Also I've heard that on machines that have password protected OF, resetting the NVRAM (called P-RAM in Macs) three times in a row will clear the password, But I've never tried it. To clear the P-RAM, hold down "command-option-p-r" during boot untill the start chime plays again. Three consecutive clears will require holding the key combo until four chimes have been heard.
There's lots of info available on the Web for OF commands, but some usefull ones are "boot/dev/...." where "dev" is the name of the drive and the path follows. almost any device detected by OF can be booted from, even from deeply nesested folders, as long as the path points to a valid boot file ("mklinux.c" for example). just "boot" uses the default boot device, usually "APPL-ROM" or "hda0/system folder("system" on OS-X)/etc/etc..." "words" is another good one to know, it'll list the commands supported by the version of OF the machine is running. OF uses standard *nix device names, except for the APPL custom chips. (example: hda0 is IDE/ATAPI MASTER (Bus 1) Partition 1(0). and sdb3 is SCSI drive 2, (Bus 1), partition 3.) for machines with two IDE buses hdc* and hdd* are bus 2 Master and Slave respectively. But if you didn't already know this maybe you shouldn't be fiddling with OF
Openfirmware is much more complex and MUCH MUCH more powerfull than IBM-PC style BIOS and care should be taken when fiddling with it. Unwise use of OF could do silly things like TURN OFF THE CPU IN PRAM (requireing a replacement ROM), or ALTER THE MEMORY AND PCI CONTROLLER ADDRESSES. Be carefull folks, but have fun!