Since you describe yourself as a novice, the easiest but most expensive solution would be to buy an External Firewire CD/DVD burner. There are also External USB CD/DVD burners. The Firewire are far more expensive. The built-in USB ports in the G4's are "USB version 1.1", which is referred to as "slow USB". You could buy an add-in adapter board to provide "fast USB" ports, which is called USB version 2.0. Most USB Expansion (add-in) cards provide two or four ports. There is virtually no equipment manufactured with slow USB anymore. USB 1.1 is rated at 12 Megabits per second. USB 2.0 is rated at 480 Megabits per second, so you can do the arithmetic. USB2 and Firewire 400 are roughly about the same speed. It is not very practical to burn DVD's with USB 1.1 It might work, but it would take forever (like an hour or two to burn a full DVD). G4 towers are fitted with Firewire 400 ports built in.
Another option is to install an INTERNAL CD/DVD burner. This is by far the least expensive solution, and in most cases it is fairly easy to install. All you need usually is a medium (#2) Phillps screwdriver. Just follow the instructions, or look them up on the web for your model of G4.
So, to review, you have basically three options. The best and least expensive is to buy an internal burner. You can get these starting at $25 to $35. It would be hard to spend more than about $80 on this option. The next solution is an External USB 2.0 burner, combined with installing a USB 2.0 add-in card. This is a medium cost solution, and requires a small amount of knowledge and skill, the same as the first option.
The last option is the easiest and the fastest and the simplest, but also the most expensive by far. That is an External Firewire, (or Firewire AND USB) burner. These would run $120-$200, appx.
Just REMEMBER that if you don't already have an aftermarket USB 2.0 adapter board installed, you WILL need to get it to utilize the full speed of a USB external drive. The combination of a USB 2 adapter card and an External USB 2 burner is usually less than an External Firewire burner.
Oh, and most External Firewire and USB burners are Operating System independant ( a few exceptions). So if yu buy one in the Windows part of the store instead of the Mac part of the store, it will usually work, assuming you have the Toast software. Most of the time the only difference is that with the Windows burner you get some basic software with it.
You'll also need burning software if you don't already have it. Toast is standard. A "basic" level of Toast might come bundled with a new burner. Otherwise you can buy a full version for arund $70-$100.
