2002 envoy Rear air suspension conversion problem

I have a 2002 Envoy and am in the process of changing the air ride to springs. I bought the springs and shocks and I'm about to get started but was told by a friend that I will need to get coupling/boots? for the springs to go into. I was wondering if thats true? All conversion kits I see online, only have the springs for sale.

Also.

I just went to a auto store and bought rear springs and shocks for an 02 Envoy. Will these work OR was I supposed to get a certain type of springs for the conversion?

Any help will be great, thank you.