Tell em their dreaming. 590 bucks to do nothing is a fuking ripoff unless they are actually removing the timing cover. If it’s only rocker cover gaskets and harmonic balancer seal the labour should only be a couple of hundred as it’s only a couple of hours work at most.
Theres probably $150-180 in retail costing gaskets. Gotta remember the entire intake manifold , upper and lower and the fuel rails need to be removed. All the coil packs and plugs , need to drive the old spark plug tube seals out and fit the new ones.
I've only done them over beers and takes me a couple hours.
But there's $240-300 in labour and $150 retail in gaskets and seals.
So there's almost $4-500 before the balancer comes off.
Reason I'd reccomended the Gumtree guy that does chains is you need to pull the rocker covers off , the manifolds and the timing cover.
So all those gaskets should be included in the price. So yes it's double the quote but it should involve the entire job being done and repairing what's already and issue and giving the motor a good chance of doing another 200kms.
Sludge does these in , pick up , galleries and chains. If they have been serviced regularly and chains aren't an issue guys are getting 400k before compression Or bearing issues.