I am one to keep repairing a machine until it is absolutely hopeless. I bought a new Oldsmobile Cutlass in 1978 and drove it 33 years. For the first 10 years, it was our road car. It then became an around town car
A lot of whether it was worth putting $3000 into your 2000 Camry depends on how you use the car. If you are making cross country travels or long distance commutes, then maybe a newer vehicle may have been a better way to spend your money. On the other hand, if this is an around town car, then the $3000 was probably justified. If the undercarriage isn’t rusted, then I would go along with the expenditure of $3000. You know this vehicle and you would be hard pressed to buy a serviceable vehicle for $3000.
One potential problem: if the vehicle is totaled in an accident, the insurance will only give you book value for your Camry. The insurance company will not compensate you for the $3000 you spent on the vehicle.
I essentially, though, am in agreement with your decision. If a vehicle isn’t rusted and parts are still available, $3000 is not a lot to spend on keeping the vehicle in service. My brother has a 1999 Ford F-150 pickup truck. Over the last year, he put $2500 into the truck–new tie rods and ball joints, new tires and some transmission work. He couldn’t get a replacement truck for $2500. His truck probably has over 200,000 miles. The engine runs well and it uses no oil.