replacing back hatch sensor

Does anybody know how to replace the back hatch (trunk) sensor on a 1999 vw beetle? The alarm keeps going off and the guy at the dealership said that it must be a sensor that the alarm is hooked into which is going bad. I have noticed here in the last few days that while driving the light comes on saying that the back hatch is open then flashes right back off so I am assuming he is correct. ANY IDEAS? The dealership only wants like 30 bucks for the park but they want $130 for installation of the part.

no idea on your car but they are usually very easy to swap out. Some are an actual switch you can see and some are part of the latching mechanism. You'll just have to take a look.