well heres all the big pieces u'll need to replicate this.
Pitbull for unit frames
eePanels for texture behind bars
Bongos for action bars
Cycirlced for spell button skins
Prat for the chat/log
SimpleMinimap it looks like for minimap, could be anything though.
Autobar for the consumable buttons in the bar above the combat log.
Markbar for the raid mark buttons
Omen for the threat meter
DamageDone for the damage Meters
Fubar for the... fubar? along the bottom.
Closetgnome for the outfit switcher thingy.
Clearfont2 to change the in-game fonts
and! probably the sharedmedia pack for the extra textures for the bars and fonts on the Unit frames. The hardest thing will be remaking that background, because thats something you'll have to custom draw yourself in gimp or PShop.
Good Luck, hope I helped