Need some some help/experienced opinions.....love this forum...first time posting.
Wife parked car at home, 420SEL. No problem as far as she noticed....next day car won't start....will turn over..no start. She tries starting the car in a span of 5-6 minutes...stops.
She calls me....I tell her to call a mobile mechanic...to diagnose the problem. He's fixed a vibration/tierod problem before/ done a tuneup/ looked over the car etc. about a month ago. I've been looking for another mechanic in addition to the one who's done some minor work on the benz because he is pretty busy most of the time.

He checks the engine at the house....wife calls me with diagnosis... no compression at passenger side of head....timing chain problem....most likely valve damage.He will fix t-chain,damaged valves replaced..$4,500..WOW.Has car towed to his place..calls next day..waterpump needs changing..$400 add...$4,900.
2 days later, calls again..more bad news...found a broken piece of the guide railing left side/passenger side.
Bottom line....add $2,000 more for total of $6,900..BIG WOW!!!!
Does anybody feel sorry for me yet I ask him where are you at as far as teardown....he says valve covers/manifold etc.
I also ask him how much to I owe him at this point...he says well at this time for his labor $2,000.
That is the excact amount he wanted upfront before he left the house...surprise,surprise.
I tell him tow the car back to the house.
Explaining the problem as best as I could above....can this much damage occur to the heads/valves turning the engine over for 5-6 minutes maximum to try to start??????
Remember, wife drove the car home with no problem according to her, parked it and could'nt start it next day.
Mechanic????? showed me the broken piece guide rail but come on now.
The car wasn't running/driving and all this damage????? $6,900....

Any toughts and opinions are greatly apprecciated.THANK YOU!