The sensor for the temp gauge in the 96 S10 4.3L would be the sensor located between #3 and #5 spark plugs, it has one wire plugged to it. The temp sensor for the ECM is located next to the thermostat housing, it has two wires plugged to it.
The clutch master cylinder on a Chevy S10 is replaced by disconnecting the metal lines, unscrewing the retaining bolts, and removing it from the housing. A new master cylinder can then be put into place and reattached.
Chevy did not use a crankshaft sensor in 1995. If it won't fire then I would check the ignition module in the distributor and more then likey replace it. Also check the ignition coil and WIRE / coil wire.