2007 1.8 T-spirit model

Can anyone please advise me. This is my first time on this site (recommended by my brother).

I had been having some trouble getting the MMT gearbox to "find" 3rd gear and it was often missing it. Also I was hearing an occasional beeping noise from the passenger side which seemed to bear some relation to the times I was changing gear. I went to Toyota to ask about it. They wanted £800 + VAT just to open up the gear box to diagnose the problem - that's not even including any parts and labour to actually fix the problem!

I have had the car from a year old. Run it for 8 years (and over 130,000 miles) and had no problems other than the general maintenance stuff like tyres and brakes etc. But the high mileage and age mean the car's probably only worth about £3K at best. Seemed like a lot of money to be throwing at a low value car.

Now the beeping is very frequent and the car is really sluggish and needing high revs to get it moving.

Can anyone PLEASE help me with some advice??