"So I have a g4 quicksilver tower. The on button shows power, the 17" apple studio display shows power, but nothing else happens... I'm not sure were to look next?"
Have you checked the internal motherboard battery? They do run down in time. I believe it is a 3.6 volt lithium "half-aa" size. They can be found at Radio Shack (part number used to be 23-026), or online for a little less money.
Before you replace the battery, look for the Power Management reset button. It's a small red button in a square black casing, probably near the battery holder. Press it ONE time and hold it down for about 30 seconds. Then try booting again. This worked for me one time with what seemed to be a "dead" computer, snapped it right back to life.