1. Get the GWX mod.. forget about getting the JSGME (JoneSoft Generic Mod Enabler) as it's included in GWX.
You also want the Torpedo Damage Final mod as well. You can get it here. It makes realistic damage on ships !
http://hosted.filefront.com/OceanBlue
You don't want to leave port without it. Also, you need Silent Hunter III Commander so you can use the GWX milk cows properly and you can also use it to alter game settings far and beyond the options the game itself gives you.
http://www.users.on.net/~jscones/software/products.html
(Make sure to follow the instructions in the GWX manual for using it with Silent Hunter III Commander.)
Happy hunting !