If you have an unmodded install, yeah, you can copy it straight over.
Extract it to a separate directory first to be sure of the folder order. then make sure the mod data folder overwrites the data folder in the game.
Or you can just use jonesoft generic mod enabler...
In case you've never heard of it:
http://members.iinet.net.au/~jscones...ucts/jsgme.zip
put the exe in your sh3 root directory.
Create a new folder in the root directory called mods, then place all your mods in that.
all your mods must follow this rule:
silenthunteriii/mods/"mod name"/data
Then run the enabler and activate the desired mods, or deactivate them when you no longer want them.
Make sure you take the mods out in the reverse order you put them in.
I've got U-boat War Ace to work with Grey Wolves as well if you want the details...