XML Editing: of Fonts, Action Buttons, Minimap, & Chat Boxes

[Dhaos]

Hello, I am at a loss at how to do the following via xml:
1)Change the font (from the default say to lucidia console) of a given string.
2)Change the font size of a given string.
3)If I want my Addon to overwrite, or rather replace, the default interface, do I simply Hide() blizzard's various default interfaces and only make mine visible at any time? Or is there a way to modify the originals?

*Please note I have done a length search on the above questions, I just can't find the information or get what little I did find to work.

I am also curious if any of these are possible via xml/lua:
(these are things I wish to delve later)
A) Change/Show the minimap as a square instead of a cutoff circle.
B) Create a cleaner skill/ability viewer. (I don't want to see shadowbolt rank 1-5, just whichever one is my highest) Perhaps a drop-down or edit box would be hand to switch which version I'm using... if I could ever think of a non pvp reason to.
C) Create a cleaner tabbed profession interface. Tabs (for major categories) instead of those nasty collapsible lengthy lists.
D) Is there a quick and dirty way (without using someone else's addon) to shift DEFAULT elements around via xml? (I was hoping to have the chat and character/minion hp at the very bottom of the screen with action buttons etc above them.

Thanks for any and all help I receive, I'm trying to learn all I can right now so pretty much any guidance is greatly appreciated.

[Seerah]

Moved to proper area of the forums.

Take a look at wowwiki if you haven't yet, and other mods (even if you don't want to use them) to learn from their code.