If you have a heavy enough floor jack to keep the body suspended high enough to stretch the airbag to full length, you'll need it. Jack up the body. In the Peterbilts, I can't remember whether the air line goes in from the top or the bottom... if it's that air ride suspension specifically designed for dump trucks, probably the top. The air line should be connected with a quick connect - stick a slotted screwdriver into the outer sleeve as you push in the air line, until you click the unlocking mechanism. Once that's done, it should expose a hex nut. Unbolt that nut. From that point, you should be able to remove the air bag by turning it counterclockwise. Install the new airbag, and follow the above steps in reverse order.
No
Find someone who'll employ you once you have a CDL, and will offer their truck for the road test. It doesn't have to be a dump truck. You could rent a 33k single axle truck from Penske with an automatic and air brakes, and, according to the DOT, it would qualify you to drive a Class 8 dump truck.
Close the rear-end air dump valve, and the truck will level itself.
Check for proper air pressure in rear tires.
Air force form 1098
The brakes will remain on, air pressure is required to release the brakes
4 Cubic Yard Front-End Loader, 8 Cubic Yard Dump Truck, Hydraulic Excavator
To give an example.... when you pave something such as a racetrack, you're at a very steep angle which would cause a dump truck to tip over once its bed was raised into the air. In many cases, the bed may not even have to be raised for this to happen. One method to allow dump trucks to dump into a paving machine on such surfaces is to have cranes hook to the beds and chassis of the dump truck in order to prevent them from tipping over. Which is fine, if the truck has a bed which won't be damaged by the hooks. However, many dump trucks do not, and their beds may be susceptible to damage from having a crane hooked to it - especially in the case of dump trucks which have lightweight aluminum dump bodies, rather than steel dump bodies.
The question is far too vague to answer. We don't know the make and model of the dump truck, we don't know if you're referring to an actual button or a knob of the type used in the air brake system of an older vehicle, whether it's OEM or aftermarket, etc.
Truck dealerships, the Truck Paper website. Careful what you buy - a lot of so-called dump trucks are just road tractors with a dump body slapped on.. they don't have the heavier duty axles, they have air ride suspensions (rather than the chalmers, camel back, or Hendrickson walking beam suspension like a vocational truck should have), they don't have the double frame, they're geared too high for sitework use which takes you off the road, etc.
In the AT/LT series, it was behind the driver's seat, contained within an air manifold which was covered by a plastic cover.
Disconnect the air lines to it, unbolt it, installation is opposite of reverse. You should be able to look at it and figure it out.