Welcome back aboard. I think I beat you to it by about a week after having played SH1 and 2, Silent Service and Aces of the Deep in my time.
No matter how much prep you do you will die a lot in the beginning. Fire up a career in auto targetting mode and go out there and sink a few fishing boats. The escorts will probably kill you when you attack a convoy way before you even get into firing range. Their sonars seem to work on ESP. Don't get disheartened. Start another career and bone up on using the manual TDC using the links found in the Skipper's Bag of Tricks thread. I seem to remember there is also a link there which explains the AI's use of sonar and how to avoid falling foul of it to often.
The upshot is that there is no real alternative to experience. Go out there and get killed. Pretty soon you will come home with a broom on your conning tower. Just don't rush it too much and don't get disheartened.
Just off to bed now to read Hitman's Manual Targetting Tutorial (linked in the Skipper thread). See you in Pearl.
PS. Read the TMO "manual" it details the additional levels of realism the author has incorporated into the game.
