The stalker quest is not essential, though it is required if you want to get into the easter egg area (well actually there are other ways in);
Larian/Silver armour-screenie-spoiler

Kiya's web site changed, so links to 'www.kiya1.via.t-online.de' need to have the 'via.t-online.' removed for the links to work (ie 'www.kiya1.de'). Alternately, check her site for the screenshots.