I did both mine a couple months ago. Failure is confined to the plastic pinion/rack gear assembly between the motor and headrest. The part is called a "headrest guide" (PN 124 970 02 26) and cost around $16.50 from Fastlane.

The difficult part of the repair is removing the seat rear cover. The first time removing the seat rear cover can be a real pain.... but doable. Everything else is easy.

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95 E320 Cabriolet, 169K