Not hard to fit mate, I did it on my Petrol FR but with an oil temp gauge not pressure.
I didn't find a whole to put through the cables/pipes from the engine bay inside the car so what I did was to remove the wiper arms and the motor (have good access) and drill a small hall close to your A pillar from the engine bay side.
Remove the plastic trim underneath the dash so you can have access to pull the cables through.
For the boost gauge just remove the engine cover and u'll see the pipes. Just cut and enter your T piece and then reconnect them. I assume you know or have a diagram of what you need to chop and where to connect???
For the pressure gauge can't
help but I'm sure someone will come along sooner or later to
help