I want to put a kind of a wiki with descriptions about technical words into my site. To do this I should have a new sidebar, only viewable in the wiki. This sidebar should replace the normal sidebar.

How can I create a new sidebar?
And how can I combine this sidebar with the wiki-sites-plugin?

Homepage: www.pronatur24.eu
Wiki: www.pronatur24.eu/lexicon
Plugin: http://wordpress.org/extend/plugins/...ki-dictionary/

Is it possible to create such an extension as a kind of plugin so further updates of atahualpa are still easy possible?

You could perhaps use one of the inner sidebars for the wiki and then use either the theme options or CSS to hide/show it where you want. I have also seen some plugins that let you create sidebars for pages.