Not hard. If electric you install the sending unit in the brass block where your turbo oil feed and stock sender is. Run the signal wire to the gauge, plus power for lights and ground, you're done.
If mechanical, I am assuming you run it out of the exact same spot, hard line through the firewall, same wiring for light/ground. I have an electric autometer gauge and sender I will probably be selling, but if I were you, I would look at the Stewart Warner gauges, mechanical or electric. They are pretty nice. The mechanical oil pressure goes from 0-100 psi in 2psi increments, so it shows actual reading for low oil pressure readings.
Summit part number SWW-114518 for $45.95
I have low oil pressure issues right now so I will most likely go with this one.