right this is gonna be a noob friendly tut (hopefully)

things your going to need

Xextool
a default.xex from your game

right get your xex into a new folder
put xextool into the same folder

now click start and type cmd
go up to command and right click and copy

paste that into your folder that contains your xex and xextool

now drag xextool into the cmd prompt

that shud pop a new window up now

now type xextool -l default.xex > dump.txt (that will create a text file in your folder will have all sorts of info
thats for if your gonna load it into Ida Pro (but we not gonna so )
now type xextool -c u default.xex and hit enter
should now be uncompressed

then type xextool -e d default.xex and hit enter

now it should say its unencrypted and uncompressed

happy days now ya can fire it into a hex editor and try find some mods in it
or run it thru ida pro and see what ya can get goin thru that