The fuel line that goes from the motor side of the shut off valve to the fuel filter is secured by a banjo bolt. There is a small lime colored o ring at the end of the banjo bolt. Buy one of those when you get your fuel line. Mine broke when I removed the banjo bolt, and I had to make a special trip to the dealer to buy a new one. When you change the fuel lines, put a new o ring on the connection between the shut off valve and the injection pump. That o ring causes lots of problems.

Check your shut off valve for cracks. You can do that by wiping it off and inspecting it and then trying, as best you can, to fill it with diesel fuel.

While you've got the intake manifold off, you should consider changing the glow plugs. The added cost is about $90 for the glow plugs and $50 for the reamer. There is a Pelican wiki paper on changing glow plugs and several instructive threads in this forum. Read the threads, because you can run into big trouble if you break a glow plug trying to remove it.

Also, the temperature gauge sender unit is under the intake manifold. If your temperature gauge is acting up, you may want to change it.