Well, for the first one Ptarth was working on something like that for a time. The thread is:
http://forums.demigodthegame.com/370367/page/1/#2459670
You may wanna check with him and see if theres been any kind of new discoveries...because his last post things only kinda worked.
For the second one, Photoshop should be able to handle .dds files. I can't remember if there's a plugin that is required though. Not so sure about free programs to edit them, but if you poke around some of the discussions involving textures, you should find some better details.
On the final one, there just isn't a simple answer for that:) It will take quite a bit of work, but check out lua/ui/game/screen_shop_tabbed.lua for how they did the item shop.
GL...you've got quite a bit of work ahead of you on those:)