Ive done a ton of these, do the three guide rails, and the tensioner rail with tensioner and chain and it will go 250 k thousand miles before needing a valve job, the chain is done by cutting a link using a guide tool and with sparkplugs removed roll in a new chain connect a link and your done about
5 hour job plus or minus, see how much your timing is off set to tdc and check marks when cam marks align , read your crank when both cams aligned you should be about 5 degrees stretched at your mileage, I would do the work, if not and the guide rail breaks it causes chain to jump a tooth or two and bam bent valves!