So I played through the fourth training mission again last night, and I successfully sunk a giant merchant ship (which was just over the 10,000 tons that I needed)!
I then started to play through the dynamic campaign, my first mission being a photography mission (sneak in and photograph an enemy dock). I took the photos, and managed to sink three merchant ships on my way out of Japan. As I'm heading home, what should happen to cross my path but two Japanese warships! I dove to periscope depth and came to a full stop (they were literally right in front of me). I let the first one pass by, then fired four torpedoes at the second one. Needless to say it was instantly destroyed! I dove for cover and headed home.
Being overjoyed at my success, I made a classic rookie mistake (overconfidence). I surfaced, hightailing it for home. Turning on time compression, I was making progress. Next thing I know, however, I'm being attacked by a lone warship that had spotted me on the surface! By the time I realized what was going on, my ship sank and the game was over (with no recent save points in sight)!
I replayed the mission, this time unable to sink a warship (though I sank five merchants). Needless to say, I headed home much more cautiously.
My next mission for tonight is spy insertion: I can't wait!
By the way, how does one receive the "Wounded Medal"? I got it at the end of my first campaign mission, but I don't recall receiving any damage to my ship. So how was I wounded?