You are not going to pull the engine out and strip it just to replace the rings, they are very cheap though about $220 from Nissan , cheaper aftermarket, pistons about $700-800 from Nissan, cheaper aftermarket , gasket set $300 from Nissan, timming belt $100 , water pump $130, bearings $250 , oil pump $500.
Then you have all the machining and labour to r+r the engine, strip and re-assemble. All up from about $6k up , depending on what parts you use and what you find when you strip the engine.
First its going to cost you heaps in labour and secondly if the rings are stuffed more than likely a lot of other stuff will need replacing as well.
A full rebuild is on the cards for you