How many miles for a manual transmission fluid change? 2003 Cheverolet Cavalier

Manual transmission? Only after 250,000 miles when you do a normal rebuild. Automatic, it is recommended every 100,000 miles. Just have the oil level checked about every second oil change or 50,000 miles. If you detect any leaks, sooner. Why the repairs? Did the transmission run out of oil? If so, did the bearings get replaced and have you checked if they are set and making a proper seal? I went through several Ford transmissions with an aluminum body that due to heat and vibrations got warped and would not create a seal around the rear bearings. The oil ran out and the transmission bearings froze. So the real answer, every oil change to make sure there is no loss for a while.