Removing the manifold isn't too bad and makes the glow plugs much easier. Take a few pictures of the fuel line routing and all the connectors / clips. You may want to pick up a few replacements. Get a hex socket and T-handle wrench with the ball shaped ends. Some of the bolts are very close to the intake runners and it is difficult to get the hex in square. The ball end allows to turn them with the wrench at an angle. You will need a new intake to head gasket also.

When/if you have the manifold off it can be a good time to de-gunk it. I got some spray "intake manifold cleaner" - the can looked like carb cleaner but said it was for intakes. I probably got 80-90% of the crud out in 30 minutes of spraying.

Chuck