Where is the PSOM located on a Ford F150 and how do you replace it?

I need instructions for locating and replacing the PSOM (Programmable Speedometer Odometer Module) on a 1995 Ford F150. If someone could walk me through it I would really appreciate it.Where is the PSOM located on a Ford F150 and how do you replace it?It would be very hard to ''walk'' you through it....you should get a manual from one of the parts stores.