Woody,

Shop prices. If the air bags cost $150 (round numbers) the drive axle uses 4 so you have $600 in parts and the labor to install should be 4 to 6 hours so on the high side you should expect to pay around $1350 total for the job. Get a firm quote.

In FL you can get a quote from Coach Worx also and my guess is the price will be very much in line with the actual cost of labor and materials. Changing air bags is something that provides a huge benefit relative to the cost. Failure to do so with the result being a blown or failed air bag results in a very expensive trailering or tow job, plus you still have the cost to replace them.