I own a 2020 MB GLE350. The check engine light was on.

• On 2/21, I took it to the dealership. Due to the P06DA00 code, they recommended oil pump valve and harness change. As the cost was expensive, I was shopping around for a specialist shop.
• On 3/3, I dropped by the repair shop.
• On 3/6, I went to pick the car. Right there, the check engine light was on. It was not a good sign but they cleared the code and I drove away.
• On 3/7, the light was back on. They asked me to come back after the weekend.
• On 3/8, I was driving in freeway and the car broke down. I noticed the engine sound was off since I picked it up. Before the car broke down, a reduced oil level sign came, cruise control was not maintaining, smoke came from the hood when hood pulled over.
• On 3/10, they report that the engine has seized. There is a hole in the block between the 2 and 3 cylinders.

That is the history. To me, the repair shop messed up. They claim it wasn't. So,

• I want a neutral party to assess what caused the breakdown. So far, couple I spoke to think its not possible. Is it that hard to identify if the repair shop contribute to the failure?
• What recourse I have against the repair shop?
• Replacing the engine will cost ~15K. Thats a big amount. Should I go for it or

what other options?