$400-$500 is a terrible price. A-series rebuilds generally don't need new pistons or valves. But they do need new valve guides, which are better than knurling (trying to restore) the old valve guides.

Often the existing oil pump and timing chain are within Nissan specs. So check them before buying new items.

Nissan recommends not replacing the cam bearings on a standard rebuild.

That kit is for forklift A15s which have been hammered every day for years. It would be better described as a remanufacture kit.