Cat,
The airline feeds into one of the retaining studs on the top of the bellows. One of those studs is larger than the other and is hollow. Shouldn't have to remove a panel to get to it.
Firestone part number is is W01-358-5406. Gm number is 665622. Mohawk lists them under that part number, superseded by # 662743, for $105.95, but they're showing 0 in stock. I bought one through the local Kenworth dealer a couple of years ago and paid about that IFIC. Shocks should be $35-$40 each.
Bob