Welcome, Neon!
Congrats on your SH4 purchase- you're going to love it! Before SH4 I had no knowledge at all about submarine ops. in the Pacific. It inspired me to read several very good books on the subject (Silent Victory, Thunder Below, Wahoo...) and you'll find, as I did, that submarine warfare in the Pacific was every bit as fascinating as the U-boats in the Atlantic.
Regarding tips for noobs, just dive in and get your feet wet. Once you've played some, you'll have some more specific questions and the folks at this forum will jump at the chance to help you out...most of 'em anyway :rotfl:
If you'd like some very general advice I'll offer my .02 and say: Dive when you detect aircraft, don't waste torps on destroyers, listen to good WWII era music during patrols, and keep a fine bottle of scotch handy to celebrate any significant sinkings (or a good ginger ale if scotch isn't your thing). Most of all, have fun and enjoy!
Good hunting,
Howler