I replaced both head gaskets in february. There is a weakness in the gaskets that causes them to erode and finally fail. If one has blown, the other is not far behind. Did not remove exhaust manifolds, unbolted them at the catalyst, and used new gaskets. Suggest dropping the sump, it is simple, and mine had a lot of sludge in it.
Image 2114 shows the blown gasket, cylinder second from right.
2116 is a close up.
2117 shows the unblown side, and the failure of the gasket material, allowing water inside.
2121 is the remains of a bolt which held the large chain tensioner. They look big, but are a weak design.