the oil pres. install depends on if your guage is electrical or mechanical. (pres. tube or wire) Mine is mechanical so i had to go to ace hardware and make a brass t-fitting, one side for the stock sensor and another for the guage. to make a fitting you need 1/8 inch tubing. its pretty simple install, just alittle teadious, you will have to drain your oil to do this.
Water temp is alittle harder, you cannot just tap into the stock sensor or atleast thats what i hear, you will have to drill into the engine, next to the stock sensor and install the temp sensor there. some people have welded a new port on the side of the motor to ensure good threads on the sensor.