How hard is it to rebuild a 2003 sohc ford 4.6l v8?

i want to rebuild the motor in my 03 crown victoria its got 122000 mile i am sensing from the engine its time the car was a university wisconsin cruiser factory it puts 250 hp when i am done i want what an American car should put out some were around 390 to 400 hp how ever i have never rebuilt a 4.6l ford in my life i have done regular ford v8 with 4bbl carb's before i just what to know what i am in for the two cams and efi and coil on plugs any help would be appreciated