If you're in the USA, hop down to your nearest Wal-Mart or Best Buy, and get SH4 Gold there. Gold is SH4 with the patches, including 1.5 U-boat Add-on, already installed. Some seem to think it's a waste to buy SH4 twice, but even if you already have it that's the quickest easiest way to get 1.5.
[edit] Almost forgot...WELCOME ABOARD!