Nicu

I'm in Vancouver, BC. The first shop suggested to start with the dealership as they may have factory recalls. No such luck. I'll explore the short block option. Many thanks.

I own a 2006 Legacy wagon, 2.5 automatic, BP, EJ25. I got a blinking CEL, error P0304, compression 0 psi in cylinder 4. The others cylinders do 165, 170 and 190 psi. The error came as I was driving up a long hill and I stopped in less than 2 km. There are no weird noises and the engine did not over heat. Subaru dealership gives me two options: A. replace motor B. open the engine and diagnose further. They say option A is min $2K, option B starts at $500-for labor alone, plus parts, depending on what's damaged. The car has only 54k miles, never towed anything, and was always maintained on schedule (I am the original owner), never driven in extreme conditions. First I took it to a nearby service for spark plug replacement, but only after they put new spark plugs told me how serious it is and I towed the car to Subaru. Questions: 1. are there other ways to assess the damage without opening the engine? i.e snake-camera, etc. 2. is there any chance that the first dealer damaged my engine by not getting the correct firing sequence after they replaced the spark plugs? Other sources indicate that is very unlikely but just wanted to make sure. 3. is it worth to go at the first service and ask for some money back since they didn't diagnose the problem correctly and charged me to replace spark-plugs? Many thanks.