If the engine is as good as you seem to think, then just a garden variety 'major overhaul' will make it like new.

The crankshaft bearings will need to be oversize ONLY if the crankshaft has been ground to an undersize. Measure the crank, & if it is within specs, & it is still standard size, then a new set of bearings from either one of the major national parts houses, or your Nissan dealers parts department will be just the ticket.

Again, if the oil pump is worn, or damaged, then repair or replace it, but if the rest of the engine is good, then the chances are that the pump is good too.

If the bores are within limits, then piston replacement is not usually necessary, but new rings are a good investment.

The best thing you can do is get yourself a workshop manual for your car & read it carefully. It should tell you all you need to know to successfully overhaul your engine.
These are such simple & straightforward engines that you should have no trouble with it.