How do you replace a heater in a 1988 VW Golf?

I replaced the heater core in my 1989 Golf. If it's the same, you have to lie in a very uncomfortable position (I eventually removed the front passenger seat even to be able to stick my head under the dash) and just start removing the interior trim and plastic vent duct work. Then you'll see a black plastic box, a little shorter than a cereal box, at about the center of the dashboard. Unclip or unscrew the fasteners holding this box to its cover, maneauver the box out from under the dash. Inside is the heater core element, which you can replace (about $30). But, It's such a pain to remove and replace all those dash components, though, I'd make sure it's really a bad heater core (and not something else like one of those blue or green sensors in the engine compartment, mounted on the heater core inlet, before I put a new heater core in. Also, I heartily reccommend a Bentley Publishers service repair manual; they're expensive, but definitely worth it for the do-it-yourselfer. Paul.

Becareful, there are 2 bolts that go through the firewall (should be the same as my 90) mine would not loosen and eventually broke (they are metal embadded in the black plastic box) now my heater core box is being propped up with a hockey puck to align the venting properly, yes a hockey puck, hey I live in Canada, it was handy at the time, and too cold to look for something else.