You'll need a few odds and ends:

a little 18ga or 22ga wire
a couple wiring 'taps'
[ these are to get power to the backlight ]

a vacuum cap (about $2/half doz. at auto zone)
a little bit of neoprene tubing (goes over vacuum nipple, stuffs inside vac. cap)
[these are to make attachment at vacuum tree)

wire ties

Long handled needlenose with the bent tips was very useful in getting the tubing through the firewall. To do this, I had to move the fusebox out of the way, then with a finish nail jammed in one end of the tube (to make a stiff push-through probe, I also taped it on with electrical tape), and using the bent-nose pliers, I wormed the tubing in along the bottom of the the main wiring harness - using the same hole. Then inside the car, I finished pulling it through. It will come out near the brake pedal. Cut off the end with the nail.

To match OEM instrument lighting, I cut the fingertip off a green throw-away vinyl painter's glove (like you get at Home Depot) and slipped it over the light bulb, held in place with a rubber band.

I don't know anything about the A-pillar mount as I put my meter in a different location. Other brickboarders will have plenty of advice on the subject. You could also try doing a search on terms like 'A-pillar' and 'VDO boost gauge.'

Good luck, it should take 1-2 hours.