Welcome! Wow, an e53 facelift 3.0d with manual gearbox - that's a pretty rare beast - at least in these parts. Never even seen one. Ever. Was wondering if they have even made them.
I drive my 3.0d (with an AT) in "manual mode" quite a bit, especially when going down hills when the AT wants to shift down as soon as I touch the brakes. I can certainly see the attraction of a real MT.
Oh yeah, +1 on the GS!