Let us know what you find out. My 97 did the same thing at 163,000. I had had previous issues with my transmission for the previous 75,000 miles or so. Lots of slipping at times, less slipping at other.
The dealership took care of it early on saying that the transmission would be at about 90% and that was the best they could do without replacing it. That was around 90,000 miles. At 163,000 the slipping came back fiercely and then soon after the OD light started flashing. I talked a previous ford mechanic, who now works at a GM dealership. He said that with that many miles once the codes start poping up on the Ford transmissions they basically become junk and ultimately you are going to rebuild or replace it. I'm no transmission expert, but I picked up a used transmission for $450 and 90,000 miles on it and was able to have it put in for free. It's gone over 10,000 mile with no issues. The fluid in the old trans was about the worst smelling I had ever smelled.
Hopefully your fix will be more simple than that. Hopefully I didn't waste $450 for nothing!