I think my mechanic burned me please advise

[samlsn]

Hi guys, I recently decided to swap out my old single pattern "962" cam for a comp xe-262. I thought I'd do it myself but thought better at the last minute and hired a local machine shop instead. A week later, when I pay the 2,600 bucks and start to drive home, I don't get half way before the oil pressure drops to just above the zero mark and at the same time the temp gauge pegs high so I pull the somofa***** off the road and call the tow truck.
My question to smarter, cooler heads than mine is weather they should take responsibility? They are not accepting any part of it. I know there's some important details missing like the condition of the motor before this event, blah blah, it had under 20,000 on a fresh rebuild but the old cam had two wiped lobes.
Basically, isn't there a hundred things they could have gotten wrong that could cause this?