I will only go through the episode with major changes.

EP1: A lot of it goes the same before the fight, First Fight: Nya vs Jay, the same fight happens just a bit longer, but when Nya wins, she helps up Jay. The last fight which is Nya vs Cole, Nya becomes sore loser, and her Sword of Fire becomes too hot, and things start catching on fire. Then Papa Wu scolds them, and every event after this is the same. Also, Nya has that same to be the Green Ninja like Kai did.

EP3: When they go to Jay's parents' junkyard, Kai catches everyone instead of Nya since is a Ninja. minor changes.

EP5: Instead of Samurai X, Kai still wants to be a ninja, so instead, he is Shinobi Z, (I know Shinobi isn't in Ninjago but Shinobi is a another word for ninja so roll with it) Shinobi is a small mech, size of Jay's Lightning mech from season 4.

EP6: Nya finds out Kai is Shinobi Z, Thats the change.

EP8: A lot changes, since Nya isn't Samurai X, Jay asks where Shinobi Z is, Nya confesses and says that Kai is Shinobi Z. She isn't there to help to help Zane and Cole, since she is on her date with Jay. Jay still unlocks his True potential like normal.

After This: Nothing Major happens, just swap Nya and Kai around and remove up Jay x Nya lines and add some up one with Nya being a ninja.