If so how did you do it? To keep rear up afterward.

No. You either replace all four with conventional springs and struts, or you leave all four air springs, and replace only the faulty ones.

You can replace the front only. It involves plugging the hoses to the front and shorting the height sensors. If your into taking the risk do some searching online I've seen the instructions before, but opted to just put new air springs in.

http://strutmasters.com

You do not have to do both it would probably be less confusing but no you can do just the front or just the back.

l completed this about a year ago on my Lincoln Continental. First, l plugged the front air hoses with a screw and some silicone. Then you have to find the resistance value of the front height sensors at a neutral height. This is used by plugging in a multimeter to the height sensor at nominal height, then shorting the plug with a resistor of that value. Worked for me!