Thats a great idea. Car don't work, get a lawyer. I guess I'll just retire.
I have resealed hundreds of pumps and for the life of me I have no clue from your description what he did wrong. Never seen no pins, noway.
Why was he there in the first place? Has anyone determined which cylinder is misfiring? If he did something that caused a problem as described it should be easy to pick the cylinder.
If so check the archives or ask Donnie which cylinder catches the carbon off the EGR valve and make sure your cylinder isn't that one before you make accusations.
It would be best that you let the first tech analyze the problem. All of us will be in a real state if proof of malfeasance comes by only the chronological fact that he worked on the car and now it has a problem.
Someone needs to find the problem. I suppose in the US legal system a good lawyer can get your money whether your case has merit or not. I can't imagine anyone paying any money till the solution is found. How much would you pay?
Bosch Master, ASE Master, L1
33 years MB technician