We do offer a kit for your application. Kit 57362
is for the 2000-2009 Workhorse W-18 Chassis, which I believe is what you have. My only concern is that it states our kit is for the 18,000 GVWR only. Which is within the range you have posted, but not positive on the distinctions between the chassis.
In each of our bag kits all parts are included to allow you to manually fill the valves via shrader valves an external air source. We do offer a wide array of controllers
as well if you are interested, which I would assume would be the route you would go. We offer everything from simple manual controls to automatic and wireless controls.
Pricing wise we suggest you compare prices from our retailers
to find the best deal. Typically the air bag kit is around $300 and the controllers can range from $250 to $450 for some of our more advanced ones. These prices of course would not include any installation if you chose to have someone install it.
I will send a message to one of my contacts to double check on the kit fitting your application. I will let you know what I hear back.