What could this be

Bought this 2020 ecoboost high performance pack with 26k miles 2 months ago and is now at 30k recently started to lose coolant and get a lot of smoke out of the exhaust with a weird smell and nothing seems wrong other than the engine light with the code p302 and just says misfire in cylinder 2 I had already got the spark plugs and coils changed dealer says it’s probably gonna have to change the whole cylinder head and it would be about 6,200$ does that a normal price to charge?