Getting a new dialog on context menu

I have added context menu to nodes. I want to open a new dialog/window which should tell description of node. So is there any property/method that we should implement to get a new window/dialog on GoXam Panel? or I should dimply create new form and do my implementation there.

The latter. WPF provides many ways to do what you want, and all of the standard ways do not involve GoXam.