What kind of job is this? Few hours in the driveway or a full weekend? I've recently gotten the ticking sound from the exhaust manifold, it mostly goes away when the engine heats up a bit. I know it's only going to get worse.

 

Your gonna have to look at the actual manifolds by pulling the engine cover. On these LS engines its common for the rear bolt on either side to break of with mileage due to the heat cycles. You likely have this issue. Once you remove the manifold you will know if you can get vise grips on t he broken bolt or if it is broke off in the head. If it is, there is usually welding involved to get the broken bolt out so it could be an easy job or a real PITA. Wont know till you pull it off.