S-15 Interlock Solenoid

I am new to this group. I hope someone can help me out here on my daughters S-15 Jimmy. She could not get the key out of the ignition switch yesterday. I had a bad time getting the switch to move. I removed a solenoid from the back of the switch and then the stearing wheel could be turned as the pin lock retracted. I replaced the ignition tumbler and put it back togeather.

Today it locked up again and I took the plug out from the bottom of the consoul and pushed on the button on the buttom of the solenoid and we were able to get the key out.

My question is, can this solenoid be replaced by its self or do you got to buy the whole igition switch. Next question is does this solenoid energize as soon as the ign switch is turned. Or is it energized as soon as you turn the switch off, if so does it have a relay or what circuit does it get its power from? Is this a common failure part? May a short in the wiring cause the same problem?

Thanks
Charlie