The marker looks like an old Shocker, circa 1999/2000.
It would only have sentimental value to a collector, so you would be looking around £40-£50 max.
The hopper looks like a Viewloader Revolution. Say, £15 - £20.
Pack? £5, maybe.
As for the air tanks, remove the covers that are on them and post up photos of the dates that appear on the tanks.