the GO-7 is probably the easiest monitor to work on.
with a no-picture situation, you would want to start with:
do you have power (is it plugged in correctly, not just at the monitor but all the way throughout the wiring harness?)
do you have signal (are the video connectors in the right places?)
if these are good, then:
do you have "neck glow"?
if no, check the fuses. if F901 (the small fuse) is blown then chances are very good you have a bad HOT and/or flyback. the flybacks in these tend to go bad after time and replacements are readily available. Bob Roberts and several other vendors sell kits to repair just about everything on the GO-7.
if F902 is blown you've probably got problems that are beyond a beginner's ability to easily repair, but you can always replace it anyway and see if it was just a fluke.
if yes, you do have neck glow, double-check your SCREEN setting on the flyback controls and make sure it's turned up. if you get white, slightly diagonal lines (and just a white screen when it's turned all the way up,) but still no picture you're probably not getting proper signal from the PCB.
there's a lot more that can be wrong with it but these are the real basics.