1) Shot-gunning a problem by replacing part after part after part is rarely
a good strategy.
2) The Chilton is barely worth the paper that it's printed on. If you are
serious about maintaining your own vehicle, get the real factory manual.
CD/DVD versions can be had for peanuts on ebay. For diagnosing cruise
control circuitry you will also need a multimeter and some basic
understanding of electricity. Without a decent manual, some tools and
willingness to learn how things work, you are much better off heading to the
professionals, regardless of how much they charge.

The deactivator switch is round, about 1" in diameter. The other set of
wires at the master cylinder go to a low level fluid sensor (looks like a
stick through the reservoir). The deactivator switch is the subject of a
recent massive recall, due to rare but horrible fires that were caused by
its failure. This may happen even when the ignition is off and the vehicle
has not been driven for a long time. For your peace of  mind go to the
dealer and have that recall done. Unless the switch has already failed, all
they will do is install an inline fuse.

Having said that, I don't believe that the cruise indicator will turn on
unless you are driving the vehicle and the servo is actually in control. So
with the cable disconnected you won't be able to tell anything.
There is a diagnostic procedure for the cruise control, which consists of
pushing buttons in some particular sequence, and the indicator light
flashing responses. Not sure if this was in effect for the '96 and I don't
want to confuse you with the one for my '98, because it may not work for
you. I remember at least one version being posted here some time ago --  
Google for it if interested.