I have a 1998 Sentra GXE with 78,000 miles.  A month ago, while I was
driving to work in the rain, my car lost all it power at highway speed.  I
pulled over and the engine sputtered a bit, stalled and I was able to start
it, then was kinda herky jerky for about ten miles, then appeared to be OK.
Also, the check engine light came on.  When I got to my work, it was running
normal.  I got the code from a nissan mechanic and it was "mass air flow
sensor".  He reset everything and it ran fine for about two more weeks, then
as I was driving home after a heavy rainstorm, the same thing happened, but
this time the car did not recover.  I limped home at about 25mph and the
engine would not shift out of 3rd gear.  When I finially got home, the
transmission had major problems, the car would not back up in reverse gear
(I have an automatic transmission) and it would not accelerate in 3rd gear,
the engine would just rev up high but I'd go no faster.  The check engine
light had also come on again during the drive home.  I brought it back to
the same mechanic and he said the transmission was fried and that the code
was "mass airflow sensor" again.  I bought a used transmission on ebay and
this past weekend I installed it.  It works fine and i've used the car and
it seems to be running OK.  Just like it always had before any problems.  It
appears two separate problems were occuring.  Does anyone have any
suggestions as to what happened?  Why the "mass airflow sensor"?  I've yet
to drive it in the rain, so I'm not sure what to expect.  Should I replace
the mass airflow sensor?  Oxygen sensors?  Any connection between the
transmission failure and these other problems?  Any help will be greatly
appreciated?  Thanks in advance.

Steve