First go here and get the generic mod enabler.
http://www.users.on.net/~jscones/software/products-jsgme.html this will make it easy to install and uninstall the mods.
Then go here to get the ships.
http://www.subsim.com/radioroom/showthread.php?t=156537
Notes;
Be sure to compare the verision of your game and the mod. Some may or may not work for 1.4/1.5
Don't expect perfection, do expect some little bugs here and there. When they make the ship they are putting a skin around a sub. there are limits to what they can do.