The 'Guide' / 'Wakthrough' was overtaken from the old forum.
It only reaches level 10 but of course Foucter has been answering any questions regarding the quest in the past, e.g. here. So maybe you could ask him if you are stuck anywhere...
As to the whole 'why isn't anyone interesed anymore' thing:
The game has gotten 'old' and it wasn't one with a 'huge' community to start with (unlike the Diablo series). There have been a shitload full of interesting games since Darkstone that evolved the online multiplayer thing to other levels. The gameplay itself wasn't that interesting to keep alive worshippers over decades. We can already have that from games like Torchlight or such...
Darkstone's uniqueness and charme cannot keep it in mind that long. It would be a different story if there would have been any sequel, but sadly there wasn't.