Welcome aboard.
Look in this thread for possible mods.
http://www.subsim.com/radioroom/showthread.php?t=108964
Most of them are about gameplay preference, so just play the stock SHIV a bit and see how it is to your liking. If you think something should be changed, there's probably a mod for it in the thread above.
Have fun and may your torpedoes strike true!
(cheesy phrase, I know :rotfl: )