Help identifying engine parts

[Richard 1992 SC400]

I recently purchased a 1992 SC400.  Can you help me identify two parts in the engine area?  Attached are a few pictures.  The first part is located between the A/C compressor clutch and the main engine flywheel.  It sticks out of the front of the engine.  It has a single wire coming out from a black boot.  Something is leaking out of the boot onto the A/C compressor clutch, so I would like to replace it.  The second part sits in the back of the engine compartment near the brake master cylinder.  It says Nitrogen Gas Under High Pressure.  What is it, and what does it do?  Thanks very much for your help.  Richard