This is my first time troubleshooting the machine. After confirming I have proper voltages in and out of power supply, is there a next step of troubleshooting? Do the switching power supplies fail regularly?
No prob, everybody has to start somewhere. Yes they can fail, but you just said that you measured good voltage in and out of the power supply. That proves your power supply is working.
The machine as stated turns on the marquee light and get the sound from the monitor (nothing else)but the game isn't playing blind so pretty sure there's a power issue to board at minimum.
Ok, you've proven that the power supply is working but it's still possible that power isn't getting all the way to the board. You could still have a broken wire, unplugged connector, etc between the power supply and the board.
Take another power measurement right at the PCB edge connector, or even better right on the PCB. If you see 5v/12v then you know your theory is untrue because power is getting to the board. If you see 0v then work your way backwards until you find the point where the power stops flowing -- a broken wire, unplugged connector, etc.
Always use a scientific method when trying to diagnose a problem:
1) Come up with a theory (like "power isn't getting to the board")
2) Take a measurement that proves whether or not your theory was correct (measure voltage at the power supply, at the PCB)
3) Adjust your theory according to what you just observed (like "saw voltage at the power supply but not at the PCB, so there must be a problem between the powersupply and the PCB")