Cutting the dash will be easiest if you have a dremel tool. Watch your window when your cutting, I nicked mine and there's an inch long etch mark right in my field of view . You'll have to get the appropriately coloured dash piece from someone, remove the front piece by carefully prying up all along and pulling up and out. You'll lose some clips...hopefully your HUD piece has them all still. Lay the HUD dash piece over where it clips into the dash and draw a close outline around the piece in fromt of the driver with white chalk. Take the dash peice out and draw another line about an inch inside of this line. You can now do anything you want to the dash inside the second line because you know it'll be covered by the dash piece. Cut out the dash roughly in the shape of the pics below, keep a rag or shopvac nearby, it's messy business. You'll have to punch holes and cut some of the dash pad out from around the three areas where the clips closest to you pop into. Be careful here as well as cutting out space for the harness since these are the two areas that come closest to the edge of the dash piece. You don't have to cut the trim right along the bottom of the windshield but there will be a clip that the part you're cutting out is attached to that will be a pita to get out. Clip the HUD in (don't worry about putting the front screws in, they're not needed), clip the switch in, turn your car on, and test it all out (speedo, dim, up/down, turn signals, radio, CD, high beams) to make sure everything's good before you clip the dash piece on.
Here's a little pic of some images I pulled out of a search:
1, 2: Factory plug locations (approximate)
3: 3 clip holes for the HUD dome clips
4: outer line
5: inner line
6: factory hole (pic is stretched vertically)
7: HUD in cut hole
8: Done
