Toyota Repair: 92 Camry Transmission problem, remanufactured transmission, transmission problem

Question
My '92 Camry (196,000 km) has problems shifting automatically but will shift manually from L to 2 to Drive.  Yesterday, for the first time, it would not shift automatically.  This morning it was functioning properly again.  I went to my mechanic who said that due to gray gummy transmission fluid, it was likely shot and needed to be replaced.  He suggested I drive it without the O/D on for a few days to see if it made any difference.  He was hesitant to flush it as that might do more harm than good.  Suggestions?

Answer
Sounds like there is a major transmission problem especially if the fluid id discolored to this extent, I don't think driving it without using the O/D will do anything, I would either look for a reasonable remanufactured transmission or possibly a used one.