Your odometer failure isn't so much a problem but a design failure. The 299,999 is the designed high end for the odometer and my '07 (337,100 miles) has the same exact issue. Good luck in finding a new one available and the cost will be in the $500-600 range. You could swap in a used one if you could find one with low mileage that would fit but you would still have to account for all of the miles that were on the old unit. No reset option. The trip odometers still work and I use "A" for each fill up mileage and I use "B" to keep track of the running mileage since it will activate the maintenance light for oil changes. Good luck in however you decide to proceed.
That's the cost effective option. One of our 2007 Corollas is at 347,000 and the other is around 175,000. On the high mileage car, trip odo "A" is zeroed at each fill, used to check fuel mileage. Trip odo "B" is zeroed when I change oil and filter (I use synthetic and Toyota filters on a 7,500 mile cycle for my rural use, not the 5,000 mile cycle on the automatic reminder), but I do the math and record actual total mileage in my little book. So any maintenance is recorded by checking that trip odo, adding to total recorded at last oil change, then entering true total.
I do not believe the trip odometers have anything to do with the maintenance reminder light. It's not the trip odo that actuates the light. I TRY to remember to reset my maintenance light at 2,500 from last oil change, so it will remind me at 7,500, but I usually forget. Fortunately, the reset sequence for Corolla is very easy.
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