The 2N6259s are over $7 each. You can ohm out the connectors to see if they're still good. Not a 100% foolproof test, but it will reveal shorts. Note that sometimes there is a 100 ohm resistor AT the transistor socket, giving some odd readings.
Jenison may have listed a newer, alternate transistor for the assembly. I recall a listing where somebody found newer, better, cheaper replacement transistors, but not sure if the power ones were included.
Make sure the transistors in the deflection circuitry on the PCB do not have their heat sinks touching. That will surely fry things.
Confirming that you have good signal (oscilloscope?) is healthy for the monitor too. If you can hear the game playing, that's a good sign. I wouldn't hook up the monitor without confirming that.
Kerry