Porting an Addon from 2.4x to 2.5x. Couple of questions

Hey everyone,
I’m pretty new to scripting in Blender so please go easy on me.
Here it goes:
I’m looking for a way to visually display a tree-like data structure in a panel. Each node in the tree holds a value, a reference to its parent and an arbitrary number of references to children. I think the best approach to this would be a recursive dropdown menu such as in the ‘Input’ panel of the ‘User Preferences’ window.
However, I couldn’t find anything about this when looking through the UI scripts in the startup folder of Blender.
Any help on this would be greatly appreciated!

My 2nd question might be a rather simple one to answer: How can you control the order of script generated panels in a window? I’ve coded a tab bar similar to the one in the ‘User Preferences’ window and a couple of panels which are polling the tab bar.
The tab bar shows up at the bottom of the region (in my case ‘TOOLS’ in the space ‘VIEW_3D’) but the polling panels all show up at the very top of the same region.
Obviously, that’s not what I want, I want to have the panels show up underneath the tab bar.
Any ideas on this?

I hope I provided enough information about my problems. If not, just let me know and I’ll try to go more into detail.

To your second question,
I just found out, that the order of Panels in the source are reflected in the order of panels shown in Blender,
Maybe try this suggestion?

Otherwise look at bpy.types.* ( evtl. start with types.V (ctrl space) the panels) they have all an append and an prepend function …