Welcome aboard Adaru. I have installed over 40 mods to get as much out of SH3 as possible. It is really too bad that your sub doesn't roll or rock in the heavy seas. However, I'm sure someone will come up with that type of mod someday which would actually be a difficult one to design.
I have been playing SH3 every day since I was able to get it in March of this year. I just finished patrol 32 and am actually having a 'ball' even though the sub doesn't rock and roll.
It is unfortunate that one site which had a lot of mods is no longer available. It got lost somewhere and no one has been able to find it, so the link to it doesn't work. However, I'm sure the person is working on that problem. It was called "List of mods tips (updated 11-04-2006)" with the link being
http://www.subsim.com/phpBB/viewtopic.php?t=30638.
I haven't tried Grey Wolves which adds harbour traffic. But there is a harbour traffic mod available separately that you can install using JSGME (generic mod enabler).
There is also SH3 Commander, which I think I will be installing before I take my next patrol, if I can get an answer back regarding a question about that separate addon which launches SH3. I hear it is pretty good. It let's you control your crew a lot better and a lot of other goodies too long for me to go into.
Glad you have become one of the group and I wish you happy hunting (am glad I DL all the mods from the missing site that I wanted, before the link got corrupted) and may you live long and properous throughout your career as a U-Boat Captain. Robert.