This is a very good guide on how to install GWX with Steam.
I would recommend only using GWX 3.0 for now to get back into the game. After you played some time you should also add the h.sie fixes.
Than if you want more mods you can check out this thread for some good mod lists:
http://www.subsim.com/radioroom/showthread.php?t=221815
A good start is also the big guide Bl!tzkr!eg made:
http://www.subsim.com/radioroom/showthread.php?t=212323