if all you are doing is the plug well/ valve gaskets it shouldnt take very long. I have tooken my intake off about 4 times and I can do it in about 15 minutes now. But if its your first time prob umm an hour to get intake and front valve cover off then another 10 to get the rear cover off (PITA), a little quicker if your SHO doesnt have EGR.
Then actually changing gaskets about 30 minutes? But depends on how much time you spend cleaning stuff up.
Make sure you have these tools set aside for the job:
10, 12 and 13mm sockets (intake, throttle body bolts)
socket wrench w/ small extension
flathead screw driver (clamps)
pliers (coolant hoses)
torx bit for valve cover bolts
rtv recommended for valve cover gaskets
misc sockets for other things
some tips based on my experiences:
watch for the hoses under the throttle body they are easy to over look
dont roll the rear valve cover gasket, its easy to do
loosen clamps from runner to tanks when reinstalling then retighten them once intalled so they seat nice and flat
now is a good time to do throttble body bypass, etc or thermostat if theyre needed
good luck and hit me up on aim if you ahve probs, i dont mind at all attempting to help you or being bugged
aim: palmer83221