Not having the OS 9 drivers installed on the internal hard disk should not affect the ability to start up from the OS 9 CD. Try putting the OS 9 CD in the drive, restarting, and hold down the option key at startup. That should give you a list of drives to boot from, and you can easily select the OS 9 CD. If that doesn't work, well, hey, more troubleshooting is needed.
To make one big partition out of two, yes, you have to reformat, but reformatting alone won't help -- you can reformat one partition or the other, because they are like two separate disks now. You need to delete both partitions on the drive, then make one big one -- and you can do this through disk utility. Just select "Partiton" when you load up Disk Utility and you should be able to resize/reformat/create/delete partitions.