Welcome Aboard!
Check this thread for a link to a wonderful SH3 mod hosting site.
http://www.subsim.com/radioroom/showthread.php?t=171019
It is a ftp server, so you will need to use a downloader with ftp capability. Maik pointed out a free one, FileZilla. I have used it with no problems. I checked and Vanjast's real nav mod is there.