Bumper, fenders, hood, grille, and lights are all different. The whole front end will need to be replaced. Fenders MAY be the same...I'm not 100% sure as I've never had one of each next to each other to compare up close.I'm not sure if connections/wiring is identical between the two, so you'll need to check into that.
Take a look at the body section of the FSMs for the respective cars. That should shed some light on what you'd be looking at.
Body section for 2004
Body section for 2007
-The MinisterofDOOM 
|The Q of DOOM| - |The Maxima| - | Hear my Q!|
4.08 VLSD, NICO 8-way ECU, full exhaust with custom headers,
Tokico Blues with Eibach springs, Stillen FSTB, 20mm RSB, 255 rear rubber.
Some people never observe anything. Life just happens to them.
They get by on little more than a kind of dumb persistence, and they resist with
anger and resentment anything that might lift them out of that false serenity.
-Mother Superior Taraza