Hi Bill,
WSS M97B44 - coloured orange is coolant [antifreeze] to use.
Sometimes it come ready diluted but mostly comes undiluted and you mix it 50 50 with distilled water. It is always worth a weekly check when the engine is cold.
The air filter come off quite easily once you have mastered the art, as it were. There are two retaining clips on the right hand side of the rectangular box [on the diesel] and you just need to unclip them. They might be stiff.
Good luck,
Peter.