plan to take all day. really. maybe two to do everything right.
if you prepare yourself, and forge thru you'll get it done.
most people will not bother with things like the coolant hose (haeter hose size) on the underside of the plenum, but once you have it off, there is no better time.
do both gaskets, get the tb gasket do, both (was it 3?) egr gaskets, and clean the upper and lowe plenum to spotless.
do the knock sensor, oil pressure sender, and PCV while you are in there.yeah you'll have to remove the starter--great time to get a nissan reman'd one and not hassel with it again.
http://forums.altimas.org/zerothread?id=255362#4see 4th post for some pics.