I have a lifted 2000 Jeep Grand Cherokee Laredo with an automatic transmission that has 294,000 miles on it. The previous owner rebuilt the engine (4.0L straight six) at about 200k miles, and I have rebuilt many of the front and rear end suspension/drivetrain components myself. It runs just fine. But to my knowledge, it has the original transmission. It's a little rough, but it has never failed to shift or slipped a gear. I have never changed the transmission fluid myself, and I don't know when it was last changed. Would it be best to change it, or is it less risky to just leave it be? I would like to keep this car as a personal project/off-roading vehicle, so I don't mind putting some cash into it over time.