Not too bad- you'll need to pull the whole heater unit. Remove the lower ductwork screwed to the floor/ hump, drain the heater unit (as well as possible), disconnect the three hoses under the hood, disconnect the plug, disconnect the heater cables and clips, pull it out. I'd remove carpet as you'll lose coolant inside the car.

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1968 230S Automatic, Elfenbein
1975 O309D Executive Westfalia Camper Bus, Blau/ Weiss
1972 280SEL 4,5 Dunkelrot
1966 VW Type 34 "Grosser" Karmann-Ghia
1963 VW 1500 Variant Pearlweiss
1969 VW Variant Automatic, Perugruen
1971 VW Squareback Automatic, Clementine Orange
2001 E320 4Matic Wagon- Our belated welcome to the 21st century! Polar White
1973 280SEL 4,5 Sliding Roof "The Bomb", Dunkelblau.