98 Taurus Vehicle Speed Sensor

I got myself in a bit of trouble while trying to replace the vehicle
speed sensor on my 98 Taurus.  The sensor is located behind the engine
in a near impossible to get at position and is held in place by a
single bolt through a tab.  After much experimenting with extensions a
universal joints I finally got a socket on the bolt and had my wife
put torque on the wrench while I held the socket in place.  The bolt
seemed to be turning when the head of the bold sheared off.

The sensor seems to be held firmly in place with rust but still does
not operate properly.  I'm afraid to go after it again without a plan
to put the new one firmly back in place.  I can't see ever getting the
old bolt out without removing the engine itself to allow me to get at
it.  The question is, once I pull the old one out, how do I
permanently mount the new one.  Can I coat it with silicon, use a
liquid weld chemical, epoxy, ???????