All great advices....Just keep up with the oil change and you'll be fine. Toyota 4 cylinders are driven by chain so they should last the life time of the engine. 6 speed automatic transmission is proven formula. Apart from brakes and tyres which are consumable. You've got nothing to worry about. All the best!!
2002 should be OBDII compliant. So it should work with most handheld scanners. If you want to go the teachstream route. It would be a better choice since it has more functions. Especially with for newer Toyotas.
I would put the car on car stands and have a look at the suspension system. Use a pry bar to check and see anything is loose. Check and see if there’s movement on the steering rack while having someone steer for side to side. Also just check your tyres for wear pattern. Hopefully that should tells you your problem!!
Can you tell if the side latch is working?? I’m assuming the cable is pulling by a latch to release a locking mechanism. It’s either cable has come loose or lock mechanism is jammed!
The trip computer display usually has a tiny halegon globe behind it which needs replacement. If it’s idling too high. Clean MAF sensor and IAC and check for any vacuum leaks. As for scanner. Mini vci cable that comes with Techstream. Forscan is also a great software.
When it comes to such problems, You need to have a good wiring diagram and some tools like Techstream, multi meter and power probe. Otherwise you need help of a good mechanic with their Autel or Snap On scanner.
Possibly dirty Idle Air Controller. It may have carbon build up and not allowing air to be drawn in at idle. I know mechanics wouldn’t miss this . But just in case they may have overlooked. Otherwise I would get a code reader and see if there are any error codes that can point you in the right direction.