This happened on my car too - pitman arm seal was toast. It shouldn't be a big deal to have that replaced, or if you can get another gearbox that isn't leaking at the junkyard, install that yourself. I believe the directions are in the DIY articles on how to do so.

If you do replace it, make sure that the wheel is dead centered when you take it out otherwise there will be problems when you put it back in if its not lined up.

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87 300E
202k on the clock