I did mine when the truck had 10,000 miles on it so I didnt replace my gasket. However, the gasket to the turbo and the one between the block and manifold are metal and they suggest you replace them.
So with close to 40,000 miles and the extra $30.00 you might be better off getting them replaced.
Im not sure if you looked into it but you can also buy a aftermarket BD driverside manifold. The stock driverside manifold has a "crush or kink" in it factory. The BD manifold eliminates that and comes pre tapped for a EGT gauge. The BD manifold comes in at around $400 IIRC.