You can change the alternator belt, on your 1994 General Motors vehicle, by loosening the tensioner pulley. The loosened the tensioner pulley will create slack in the belt. Remove the belt and replace with a new belt.
Disconnect the battery. Unplug the alternator and take the belts off. Unbolt the alternator, and bolt the new one in. Put the belts back on it. Plug it back in and reconnect the battery. Voila! You changed your own alternator!