also late....but VW replaced my 1985 Jetta heater core for free (a current 1990 dealer estimate of $500 before I found out about the recall. As it was a health and safety recall (bursting, scalding water entering the cockpit of driver and passenger) perhaps you could be reimbursed by VW? Good luck.
PS...if you live in a warm climate you can jump (connect) the cold to hot hoses in the engine compartment before they enter the heater core. You will be without heat but save the hassle of dash removal and replacememt.
My local dealer (Fredericton VW) doesn't honour the recall anymore. I have an 85, 89 and a 92 and they wouldn't replace it in any of them. Luckily it's not a real big job if it doesn't have AC and the whole dash doesn't have to come out. I can do mine in an afternoon easily.
I replaced my heater core on a 1991 Jetta Carat a few years ago w/air conditioning.
Just an idea of what it involved.
The following needed to be removed
Gear shift top grip (not metal post) protect little wheel on top)to allow clearance for dashboard. Dash board basically needs to be pulled pulled to the seats.. Speakers stereo all out.
All little screws on dash and around spedometer/ odometer. Disconnect All electrical connectors behind dash
Speedometer needs to be disconned behind dash
Speedometer instrument panel needed to come out.
All switches headlight hazard etc levers for climate controls removed to remove dash
All bolts on the fire wall. Hidden screws near windshield wiper motorSmall Air hose grommet removed to allow air hose to follow dash
Steering wheel needs to come off
All harness wiring around the steering column and turn signal lever and cruise control. Anything connected
To the steering column
Center console needs to come out
Air ducts need to be disconnected under dash.
Water lines to heater core disconnected.
Heater core is basically behind the center console near the top of the dash. Two screws hold the heater core in place.
Getting everything to line up is tricky when putting back together, air ducts wiring etc
This is the way I did it because it seemed like the only way. But I got it fixed. One thing when I just did the head gasket and most of the coolant passages were blocked. Maybe this caused the heater core too much pressure.