RE Mods:
Mods are in a state of flux right now since we had a patch. Check the stickies in the mod forum for the 1.4 compatible list. If you happen to eyeball TM, don't d/l it yet. I *hope* to post another revision of TM tonight, so the current one will be outdated soon.
RE torpedo tracking.
If your new to submarine simulations, id recommend going with autoTDC - for now. You'll have alot to aquaint yourself with, and the manual TDC might be a case of information overload. That said, this is one the best tutorials for manual targeting:
http://www.subsim.com/radioroom/showthread.php?t=118923