wow the mechanic screwed him over and did a shitty job
so what ur saying is that he was charged 1,000 for a head gasket and timing chain set. now the noise is either a faulty chain set or the guy screwed it up putting it in. if the piston was slapping around he would have alot of smoke coming from the exhaust. as for getting it fixed take it back to the shop and show him let him hear it.
and say fix it. it only started when you touched it.