prowler3, this is what I would do:
1. Unzip "GWX 3 St Naz and Schluese and other units.7z" into your SH3\MODS folder.
2. Open JSGME (or press F5 if it is already open). You will see a new available mod called "GWX 3 St Naz and Schluese and other units"
3. Disable "GWX - Merged Campaign" and/or "GWX - Lite Harbor Traffic" mods if they are enabled
4. Enable "GWX 3 St Naz and Schluese and other units"
5. OPTIONAL: Re-enable "GWX - Merged Campaign" and/or "GWX - Lite Harbor Traffic". You will get a JSGME warning pertaining to the Campaign files; ignore it.
Pretty much as per BBW's installation instructions.
Doing it this way means that if you choose to remove the mod, you just disable it and you'll get the original GWX optional mods back.
Personally, I'm not a big fan of recursive mod enabling, but it's not a problem if you stop to think a bit about how it works...