There are quite a few good mods already out for the game. One is a campaign extender which adds a significant amount of missions to the vanilla campaign. I also play around with the Los Angeles Flight II/III mod, which introduces the VLS and MADCAP Torpedo to the game. That makes it a lot of fun, and not so much of a pita to go get TLAM's when a mission arises.
One tip, don't take too many Harpoons. They are just a guarantee that at least one helo is going to come and drop a bunch of torpedoes on you. They also have naval bombers in the game and they love to drop torpedoes too. Playing the game on the high difficulty levels requires a lot of patience and thought.