My 2014 Buick Verano had been throwing air intake codes so I replaced the MAF sensor which got rid of the engine lights. Months later the car died (no rattling, no weird noises, just instant shutdown while driving slow). It started right back up and the mechanic replaced spark plugs, air filters, and a couple sensors. He told me the timing chain is about to go and it’ll cost me $7-10k to fix today or the car will inevitable self destruct. The car never gave me codes related to timing or engine performance.

1. Is it possible to give this diagnosis?

2. Is that an insane quote?

Thanks