Any auto glass installation shop would have the optical coating. Goes on wet, then dries clear. It'* not quite as good as the factory coated windshield, but it'* cheaper. Won't distort your vision either.
If you want the hud to be totally capable, I'm going to guess you'll have at least a dozen wires to run and splice. I've never had mine out to count. Not going to for you, either, unless you shave your legs
The HUD displays the following: Vehicle speed in kmh or mph, turn signals, check gauges, and low fuel (this would be a Hud from the early 90'*) There are also different huds for adjustment. 92/93 were a mechanical height adjust, 94-96 were electrical (more wires to splice, but you could mount the controls just about anywhere without being restricted by cable length) and 97-99. This last HUD may give you trouble due to OBDII electronics in the PCM. The 00-03 HUD would be a nightmare. Much more to display including radio frequency....what all else, I don't know. You'll have to make your choices wisely on where you mount the controls based on this info. FYI, the dealer retail on a new hud ranges from 900-1300 bucks. gmpartsdirect should be about half that price, and no telling what a wrecker would want. You need the HUD and control panel as a matched set from the same car. I also suggest a factory schematic before attempting this!