Can the classic enviornment be installed AFTER installing
osx10.3.6 ? Didn't think I'd ever want it again... but alas I
discovered some old game (s) that I'd like to play again.
Please advise if possible.

Install OS9 using the installation CD and follow the on screen instructions. If this does not work, which it might not...

The other alternative is to:

Network your Mac with another one which has a valid OS9 system folder on it. Then copy the System Folder and Applications folders from that computer to the root level of your Mac.

i just did it a few days ago.
installer works fine.

you can insert the disk then go to system preferances--> startup disk and choose the CD or just reoot anc press "C" untill the OS9 setup screen comes up.

I am having the same problem, wanting OS9 after having installed OS Panther. Pressing the C key never got the screen past the startup disc question mark. Loading OS 9 system and application files from my G3 was not successful either. Finally loading the OS 9.0 install disk and choosing it as the startup disk in System Preferences resulted in an installation that could not be completed due to "problems on target disk". Do I need to use a system 9.2 disk to try this? Would my 9.1 upgrade Zip disk be sufficient?