Weird sound in engine every few seconds

Would it cost much more to rebuild your engine with a new head?

 

I think these sorta things happen more often when the modern day "mechanic" tries to use a computer to solve a mechanical problem. Not all new mechanics are bad but boy are there a ton of stories like this.
Of course we're blessed with the power of hindsight here but man it's a shame that the OP has to foot the bill for a relatively rookie mistake by the shop he was paying.

 

Your engine has more miles, but if you rebuild the engine with new rods and mains, cylinder packs, new head and a new turbo if yours has not been replaced recently then you have a fresh engine. I’m skeptical of a used engine I know nothing about when there’s the possibility of yours being rebuilt.
I have no idea of the cost for a rebuild for that engine but that is the first question I’d ask.