I did the rear air springs myself, which were pretty easy as mentioned in this thread. One thing to keep in mind is that the front air springs are mounted on the struts themselves. You have to R&R the entire strut assembly to R&R the air spring. If the air springs are failing, the struts likely aren't far behind. MOST IMPORTANTLY--while you can buy the front air springs by themselves, the struts ONLY come with the air springs preinstalled. If you replace the air springs and a short time later the struts go out, you'll be rebuying the air springs when you buy the struts and redoing all of the labor. So, if the front air springs have failed, be sure to buy the whole strut assembly, not just the air springs.
Don't ask me how I figured this out.