I know the '94-'96 Grand Prix' were pre-wired for HUD. Although the '97 & up units look very similar, I've read they're not the same, and that they're not pre-wired. It is far from impossible, just a time staking, tedious pain. You'll need the HUD unit, the dimmer switch, the wiring harness' for both, the dashpad (which will have the cut out to allow the display to show through), and any brackets the HUD unit may require to bolt down to the dash (I'm not all that familiar with what the '97 & up units require to bolt in, if anything). Oh, most importantly, a wiring diagram for the HUD, HUD dimmer switch, and your gauge cluster. You're basically going to splice the speedo wire on the HUD into the VSS wire running to your gauges, turn signals to turn signals, high beam to high beam, etc. Like I said, it will be time staking, but it can and has been done. With the exception of the wiring diagrams, you should be able to find everything you need on eBay (though you may have to pay a pretty penny
).