Replace the core if you're going to keep the car. Plan on pulling the dash. It isn't a big deal, only time consuming. Youtube has videos of console & radio removal. There are threads here of dash removal. Steering wheel is easy (10mm Allen Wrench on 3/8 socket). Do the vac pods while you're there. FSM has details on getting to the core. Drain & flush the system - why not? you'll be right there. Take pics. Put everything back clean & tight. You'll have a nice functioning climate control that you won't have to mess with.

Save the suspension for summer.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.