I have a '95 Nissan Pathfinder, 115,000 miles, V-6 engine. The local dealer told me that both exhaust manifolds are leaking and that the gaskets and studs need replacing. My question is, what is required to replace the studs? Can they just be unscrewed from the block once the manifold is removed? And if so, does it require some special tool besides standard wrenches and sockets? Any advice on this problem will be greatly appreciated.