Firestone Air Springs

You might try taking a few pictures and sending them to the shop before you make the drive for them to "look at it". After seeing the pictures he should be able to give you an estimate on replacing the spring, which are usually replaced in pairs, and how long it would take. Two hour drive is not that convenient but it is what it is, if nobody else wants to work on it. It is not that difficult of a job but it does take a little time and some basic equipment that most shops would have.
Here is a link to get an idea of the spring cost: SD truck springs
There may be cheaper places since I just grabbed this place off of the internet.