Can someone id this green part? Z5V 104Z 500V I think maybe it's a varistor (like the blue one in the lower-right of the image) but haven't been able to find a replacement.
It's a Z5V dielectric 500V 100nF ceramic capacitor. Depending on how/where it's used (across the AC line or line-chassis) it may need to be a safety-rated X or Y capacitor so you will have to replace it with the correct type of capacitor if it's in one of those locations. Usually X and Y caps are film caps, but ceramics are possible too.