The company that makes the specialty tools for Ford makes a socket specifically for the pressure switch. But if you take the whole unit out you might be able get some channel locks on it. There is a small o-ring on the end of the switch. Replace that, but make sure it is EPDM rubber or otherwise brake fluid resistant!
If it is not the pressure switch that is leaking, it could be the gasket between the pump motor and its houseing. Two allen screws hold the pump on. Mine was leaking in December. I found a local gasket manufacutuer in Norfolk, VA called Gaskin's Gaskets.
http://www.safetyvalve.com/
I gave them the motor and the housing and I had them make me two EPDM rubber gaskets. They HAND CUT the gaskets at the proper thickness and size for me for $8 a gasket. I thought that was a great price. That was my
latest brake leak issue. The gasket worked. This company will make you anything so long as they have the size.
Also, like it was mentioned above-the gaskets where the reservior hose goes into the pump housing. About a 2 years ago, that was leaking on my because the gasket for some reason was cocked out of its seating.
I've had more that enough problems with my brake unit. And have takeing it apart about 4 times. So, if you need more help let me know. I've fixed my problems every time!
Metalman