BMW Repair: Cylinder head, stean, intake valves

Question
M3
Week of June 22, 2006 valves hit all pistons and bent all intake valves. Removed valves from original head and sent to machine shop to check all specs to see if a problem was with the head or installation.

June 27, 2006 Called and talked to Craig.  Craig said they were to receive the head. I expressed my concern about the pistons and he said the valves just touched the pistons and they would be okay.  At 2:40 P.M., I went to the shop and asked to see the motor.  As I walked up to the car I observed Benny bent over the engine compartment. As I got closer, I observed him scraping the pistons with a scrapper around the piston landing for the valves.  I asked Benny what he was doing and he said he was removing the burrs from this area so there would not be a hot spot the piston.  I asked what would happen with a hot spot and he said “detonation and possibly the hot spot could cause the piston to crack.”  He then told me he had messed up on the installation possibly not getting the time chain on correctly.  He said he has messed up before.  When I looked at all the pistons, I clearly saw where the valves had hit all the pistons.  From the scrapping Benny was doing, I could see unevenness (Scratches and grooves) on the landings and the circular insets out of proportion.    Benny then showed me the bent valves.  The valves were not slightly bent but extremely bent.  I took two valves with me.  Originally brought in for stean out the exhaust. Found crack in head and warped head.         
Sir do I need to worry about this repair procedure?
Thanks Allen

Answer
His explanation was correct although his procedure is lacking.If you found a crack its time for another head,if it was just warped as long as its not excessive can be resurfaced.I wouldn't be proud to say that it has happened before,he must be rushing his work and not taking the right steps to install the timing chain.Would I worry?.....yes