Welcome back Skipper....
I'd go for some eye candy & sound Mod's first, get a feel for the game, see where it takes you and then go for the TM x.x Mod.
Start digging in this topic:
http://www.subsim.com/radioroom/showthread.php?t=118945
Nose around in the threads in the SH4 Mod's Workshop to see what suites you and what not.
You have enough to read in those topic's to keep you going for a while.
When you have questions about Mod, don't hesitate to ask around, help's nearby.