First of all: I hope you enjoy your stay at the Fawlty Towers!
(never heard of Fawlty Trowels though....)
Second of all: This would be considered the wrong forum mate. Try SH4, not SHIII:hmm:
Now, to your questions....I happen to own Silent Hunter 4 Wolves of the Pacific: U-boat Missions already. For those of you who hizz in the background, I bought it fair and square here in Stockholm, the game has been out for a couple o' weeks already.
I don't know anything about any collectors edition, maybe I've missed it.
As far as I know, there is two new subs: IX class and XXI. They're borth beautiful and fun to use.
You can find lots of american convoys with little or none escort, so although the campaign starts as earliest in 1943, you won't be dead meat at once.
The game is alot of fun actually. Some cool new features, like being able to radio for support of different kind.
I'd say that you should buy it when it comes out (at least if you like SHIII/SH4).