1996 GT Exhaut Manifold Leaks.

First, are you certain that the leak is between the cylinder head and exhaust manifold? It is much much more common for them to leak between the exhaust manifold and H pipe.

Second, before digging in, you should try simply tightening the manifold bolts. A couple U-joints and a wide variety of extensions will help tremendously.

It is possible to get the stock exhaust manifolds out without removing the engine. You probably won't even have to lift the engine off the mounts, but that would help too. Again, lots of extensions and a U joint make it a lot easier.

+1 on above. Sears sells "flex" sockets that are basically sockets with the U-joints built right in. These can be a real God send working in tight places. Recommend getting the 6 point socket if working on exhaust bolts. I believe it is a 13mm.

A set of long extensions may prove helpful. Some of the bolts will be done blind/by feel. Try to make sure that the socket is well seated.

Be prepared to use different tools for different bolts depending upon what is in the way (crows foot/wrench/stubby wrench).

Also recommend that you pick up an extra set of exhaust bolts/stuts. In my experience, the studs are easily broken. Soak/spray the nuts will before starting work. It may save a broken stud.

It is tight working up there. However, once the exhaust H-pipe is removed, this will improve access. Take your time and take a break if you get tired.