EGR gasket should be changed. The part number escapes me at the moment, but the IAC valve gasket is rarely changed. As per Martin's experience, the manifold needs to be scrubbed with a Dremel on the gasket mating surfaces to ensure a proper fit.
As for the torquing; move from the centre outwards, diagonally opposite for the corners. I don't have the picture on-line (already checked) but it's fairly easy. Start with left of centre, then right of centre, then top left, bottom right, top right, bottom left, etc. It's easy to do. Just remember, the toruqe spec is 10Nm or 7 lbs-ft.
