i am trying to find out how to remove and replace the heater core in my 87 4 cyl sedan. any help is much appreaciated. thank you

Yea.. I replaced mine in the wagon many years ago.
The core is right in front of the shifter console down at the floor. If memory serves, I had to remove darn near all the plastic trim and heater ducting under the dash to get the panel off. Think a couple of those screws to the panel covering the core was a PITA. Oh...and you gotta crawl under to get to the hose clamps to disconnect them from the core, they are under the rack&pinion so you can't get to them from above, drain the coolant but be prepared for a face full anyways when you pull off them hoses!!
At least you got a chance to get at it B4 the cold weather sits in, that'll make the PITA a little less painfull!!

Jeff-

Want me to scan the service manual for you?