First - go here and download the 4.3.x documentation pack.  In there is the PDF on skinning, which is 70% of what your asking for.  Take the time to replicate the example (except for the graphics if you're not a graphics person).  It will show you what to do easily for #1.

#2 depends on what kind of script and what it does.  You should search on this topic in the forum search or check at forums.asp.net as well.

For #3 - this will depend on if the buttons already exist.  IF so, the guide will show this.  If not, you'll need to develop the object. 

From here, go to the skinning forum for questions on layout and design, and the Extend it forums for custom development. 

Cheers