rear air bags

yes they are easy to place jack car up then jack stands on frame lets rear susp. drop down then take off rim just turn air bag off its easy

I do not see where your Envoy is equipped with "rear" air bags. I see front air bags in the dash and side air bags in the front seats. In order to replace the side air bags the front seats must be removed and partially disassembled.

You need to have a qualified tech to do this. Also, if they were deployed, the Air Bag computer needs to be checked because some models self destruct, when activated, as a safety precaution.

Get a conversion kit from Strutmasters.com about $300.00 can be don in about an hour

Get a pair, with a lifetime warrantee, for $200 total, from Arnott. Just need to jack up rear and use jack stands. No other tools needed. Instructions come with the bladders and take about a half page with big letters and diagrams. Very cheap and easy fix to a problem that seems to vex or break the bank of so many others.