I did link you to my thread, in the other thread you had about boost gauges - which had enough pictures to get you going.. combined with the information you get with the NewSouth gauge should have been more than enough for you to do it?
In short (because there is already a very good guide on VWVortex if you have a quick google for it)
You use the t-piece and replace the existing piece of vacuum hose with this. Put rubber tubing onto outlet. Put nylon plastic tubing in this and route it to the bonnet release catch. Feed it through the bonnet release catch (use a coathanger or other piece of wire and wrap it around) then route it up to behind your dashboard...you will need to take the fuse cover off and pop out the little tray near the headlight switch.. pop the plastic surround off at the bottom of the dash just above the steering wheel.. make a little nick for the nylon tubing to pass through.. feed the tubing through. Put boost gauge in pod. Put rubber on outlet on boost gauge and put other end of the nylon hose you just fed through into the car, into the boost gauge. Cable tie all your connections. Splice into the grey wire for the illumination.. you only need the rubber bits and the cable tie the brass things, the red things (for JDM styley mounting etc) don't need to be used at all.
There's really no recipe for disaster at all. It's very simple, the hardest thing as mentioned is routing the tubing into the cabin.. use the bonnet release cable route!! I can fit them in 30mins to 2 hrs depends on how much of a pain the routing to inside the car wants to be.
