Should be a simple job - pull up ALL of the old deck tread, replace with new, and replace the handrail.
He managed to almost replace half the deck, butchered the handrail, and hasn't been heard from since.
Want to replace with 140mm decking, and maybe stain it to match the older timber underneath and on the side.
May want to go with a curved handrail - not sure depends on cost.
Not an urgent job - can be done any time but could possibly wait till early Jan