If you do not know the difference between Harpoon Classic and Harpoon3, here is a quick video showing some of the major points:
Both versions have hundreds of scenarios. Whichever version you decide to play will likely give you countless hours of enjoyment. It's the kind of game(s) where you always want 'just a few more minutes' and end up greeting the sunrise.
Welcome aboard, shipmate.
p.s. If your wife is purchasing the Harpoon Ultimate bundle of games from Matrix Games, you get both the Harpoon Classic and Harpoon3 versions in the same package for one price.