Yeah, definitely not factory. For starters, the font on those stickers looks hideous and cheap and doesn't correlate with anything from Chevy, the Lumina OR Days of Thunder. Plus the phrase "Thunder Lumina" doesn't make sense and isn't something GM would have used, so the stickers definitely aren't "official". Secondly, as @White93z34 mentioned, that is an aftermarket body kit, not a factory Z34 kit. The front and rear bumper covers have a similar general look, but there are several differences. It looks like the fronts have little cut outs for fog lights maybe? Hard to tell from the angel you took the pics, but whatever they are, that's not something present on the Z34. On the back, there is only a single outlet for the exhaust rather than dual outlets, and the spot for the license plate is in the "normal" spot whereas it gets moved to in between the tail lights on the Z34s. The rocker panel pieces are just a side skirt on this kit whereas on the Z34s, the middle pieces would be full cladding that went up as high on the door/panels as the front and rear bumper cover pieces.
As far as value, given there's nothing special about it and considering how much it would cost to restore it cosmetically and mechanically, I'd hate to say it but I don't think it's really worth anything. If it were mine, I would maybe remove the body kit and hood to see if I can scrape a few bucks out of selling those separately (the vents used to be popular for older Wranglers) and junk the rest for the most money I can get.
Sorry. I know that's not what you were looking to hear.