Dear bleu83--  It's simple.  To install the heater core on your 1988 Monte Carlo, go to the following site-- http://autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/11/cd/ec/0900823d8011cdec.jsp.  The rest is up to you.  Call me if you want me to come over to help.   Good luck from bovan.