Go to your local autozone get a basic tune up spark plugs wires and fuel and air filters have them reset the light if the light comes back on take the map sensor back to autozone to have it tested
You have it checked for codes and diagnose the cause of the code.
Check engine is an error. You have to go at a garage to see what is the error code, then correct the problem.
Sometimes this website can be helpful for decoding chevy engine numbers: http://www.nastyz28.com/chevy-engine-code-stampings.php
I can not without the manual in front of me remember which position its in but it should be either a 'W' or 'X' code, more likely the 'W' since 95% were made of this type engine, 262 CI / V6
90-9879
VIN code "H"
You must have an engine scanner to do that.
The engine codes for gasoline engines in the 1985 Chevy Celebrity: 2.5L 4 cylinder engine code R 2.8L V6 mpfi code w 2.8L V6 carburettor code x
http://chevythunder.com/199295_lt1_trouble_codes.htm
You have a 1973 nova 350
Diagnostic trouble code
its Chevy 454 Big Block Engine