[xmonad] how can I completely re-install ghc/cabal/xmonad ?

Hi guys, It seems that my ghc configuration is broken ( /usr/lib/ghc-6.8.1/package.conf ) . Is there a way to re-install properly cabal / ghc ? (or at least find a way to fix my conf) I would like to make a clean install of xmonad. thanks in advance, Lobzang.