I've cleaned it up, drained the excess fluid from the front diff, and replaced the breather (check valve inside engine compartment/driver's fender), but have not warmed it up enough to tell for sure. Will try it out in a week or two and report back.
Inside the breather is a spring and a rubber/plastic/neoprene valve. I'm not confident that it would work properly after gear oil has been in there. $5 at the dealer. 90930-03136 for 2001 SR5