Leaking emergency shutdown fitting?

We just got some new 5000 gallon liquid tankers we use for HazMat. Near the nose of trailer is the standard emergency shutdown device that looks like a bronze pencil without a point. A driver called me and asked what to do, his is leaking. It looks like it's been cross-threaded into the hydraulic line.

I'm new to tanker & never thought about this possibility.
What fluid should I carry if I had this problem?
Do drivers carry spare shutdown fittings if that's what they're called.
Can a driver remove & replace that shutdown device himself, or is it be left to mechanics since it's a safety item?
HOW & where does a driver add fluid to that system? Do you add fluid at the jack that opens the internal valve?

Thanks