That transmission that started jumping out of gear might have had a shift fork in marginal condition, and once the transmission got good and hot, it started popping out of gear. The good news is, they're not terribly expensive transmissions to rebuild. I was quoted an average price at a local tranny shop of $360.
Well, know what? That old girl is about to take another load, and a small U-Haul trailer, 400 miles to Santa Fe. Hopefully the tranny won't get hot and give me trouble, but last weekend driving 8 hours towing cars on washboarded roads without any problem at all sort of gave me confidence that nothing will happen in 6 hours going to Santa Fe.
Besides, ever notice how nice and smooth the ride becomes once they've got a load in them? Actually quite pleasant. It rides much rougher empty.