I am replacing the cylinder heads on my 05 silverado. Probably has the cracked castech head. Do I need to pull the valley cover and look for coolant in there? I have never done this before but i am down to the heads. just have to pull those off tomorrow. afraid i will see cylinders full of water/coolant. is there anything else i need to check while i'm in there? or can i just get the heads and gaskets and reassemble? thanx for any help! What is under the valley cover?