I don't have a lot of expertise in aftermarket radio/stereo; in fact I avoid them like the plague. So if you get other advice...listen to THEM and not me.
Does the radio make noise? Music, voice? What doesn't work is the DISPLAY, not the ENTIRE RADIO?
I'd expect TWO power wires for that unit--one of them constant power for the clock and station memory, one switched with the ignition that actually powers the audio section. Maybe even a third power wire that's tied to the dash lights, for dimming the display??? And if so, do the dash lights work--nicely bright? GM likes to tie the dash lights to the tail lights by putting them on the same fuse, and of course the dimmer for the dash lights could be all the way "off".
Which probably means that you're looking to verify at least TWO fuses, and perhaps more.
The old crap radios I screwed with years ago had in-line fuses as part of the radio wiring; the vehicle end of the wire was also connected to a fused power source. So the vehicle fuses had to be good, and the in-line fuses had to be good. Too damn many fuses!
If this was me, I'd grab a spare car battery (known to be properly charged), some alligator clips, and a big plastic cutting board, put the cutting board on the kitchen table, set the battery on it, and then using the wiring diagram, connect the radio/stereo power and ground wires directly to the battery. At that point, you'll know if the display works. Then you could jam a CD or tape or whatever into the thing, and if you have some extra speakers, you could verify that it plays music in air-conditioned comfort without your head under the dashboard.
When you're done, the cutting board goes in the dishwasher or gets rinsed in the sink, and there's relatively little mess.
At least that narrows the problem to "radio" or "vehicle". If the radio is OK, you know the vehicle wiring/fuses are at fault; and if you're clever, you'll know WHICH mating vehicle wire doesn't have what it takes.
Considering that the other radios also didn't have a working display, it's almost certainly something in the vehicle wiring...just a matter of tracking down which wire from the radio isn't getting power, and then checking the matching vehicle circuit.