There is no trick. Drain the coolant and go for it. It's located under and next to the monovalve. Getting to some of the hose clamps is tricky but not impossible. Remove monovalve and bracket and you'll see it behind the front firewall. You can loosen the firewall pieces for better access if you're feeling confident. Other than that its not a real bad job.

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Orland Park, IL
1985 300SD 215,000 miles