Since you said you got SH4 and the Uboat missions Im assuming your already patched up to 1.5. It was included with the uboat mission add on.
Enjoy the game as it is for a while before you start dabbeling in modding just to make sure it is stable on your system if nothing else.
Also note that most major mods really only address the US / pacific theater stuff.
Good luck good hunting and welcome !