The trans code that you have, the P0742 TCC Stuck On, has a handful of causes but since you have 100K on the clock it is going to likely require more than a simple fix to get you back to working how it should. Often the lockup clutch in the torque converter will deteriorate for a number of reasons and can contaminate the valve body and TCC solenoid, more importantly the TCC solenoid. When the solenoid becomes contaminated it will plug up the exhaust port on it and can cause lockup to apply when it isnt supposed to be and this is the most common cause of the code you have that I have seen over the years. Sometimes replacing the valve body, solenoids, and torque converter fix the problem but you have to keep in mind you still have a 100K mile trans that is showing its age and you will likely have other issues pop up over time. If you had under 75K miles I would probably suggest trying to fix it or have it fixed by a shop but with 100K I would seriously consider a rebuild or replacement. If the car is in good shape and you like the car then I would keep it and not have a car payment VS getting a new car and having a car payment 5 or more years. 10 years ago I would have gave you a different answer lol but I enjoy not having a car payment more than a new car!
