Depending on which engine you have, there are several O2 sensors on the vehicle and they are all threaded into the exhaust at various points.
After the catalytic converter.
The coolant temp sensor on a 2003 Chevy S10 V6 is located on the front of the intake manifold. To replace simply unscrew the old sensor and screw on the new one.
The 1994 S10 uses a MAP sensor, not a MAF sensor. We need to know size engine you have in that S10.
It is threaded into the header pipe directly after the exhaust manifold on the passenger side.
That should be the sensor located after the catalytic converter.
If it has a 4.3L engine the temp sensor is located next to the thermostat housing.
We will need to know which engine it has to answer that.
4.3L? Inside the distributor.
the fuel level sensor is located in the fuel tank with the fuel pump
You won't find one. The 1991 Chevy S10 doesn't have a MAF sensor.
Inside the distributor.
Top center of engine, 2.2 or the 4.3 engine.