You are right to be concerned. There are some applications and programs that do not work well in Classic.
You can safely install Panther but there are some firsts you must do.
Go to:
http://search.info.apple.com/?search=Go&lr=lang_en&kword=&q=Firmware
And check for firmware for your machine. Install it while in OS 9.
Make sure you have the full install Panther. Since you do not have OS X installed, an update CD will not work.
Start up with the Panther Disk 1 (insert CD, restart computer, immediately hold down the C key).
When the computer starts, you will get the installer screen. It is different from OS 9 as you do not see your desktop or your hard drive. Before you click on anything in the installer screen, go to the Installer menu and select Disk Utility. Click on First Aid and have it Repair Disk. You need to click on the second drive icon at the left as this is the formated drive you want to check out. In order to keep OS 9 - you do not want to format the drive, just check it.
When Disk Utility is done, quit it and you will be brought back to the installer screen. Just follow the prompts. There is one screen that will have a custom button. Select this in order to see the options of languages and printer drivers.
When done, you will be asked to restart the computer. Then it will ask for Disk 2 and/or Disk 3. When those installations are done, you will be asked to restart the computer (again). Now you will be prompted to set up a user and password. Make sure you choose to be administer. Do not forget your password. You will be prompted for it when you log in and when you install programs.
Once done, you want to go to the System Preferences - which is the light switch in the dock. Here is where you can set up your own preferences. I highly suggest you go to Software Update and get the security updates first. Also you will want to get the 10.3.4 combo update. These require a restart.
When you are done installing, go to the Utility folder and select Disk Utility. You want to repair permissions now. This is important as it will make sure you are set as administrator and be able to open programs and apps on the computer.
While OS X does take a bit of learning, you will like it. When done, you will have OS 9 system folder and OS X. In the Startup Disk panel in System Preferences you can select the OS you wish to boot in.
