2003 Envoy SLT. How much to convert air coil suspension to standard spring coils

What is your question?

2003 envoy SLT rear air suspension compressor is bad. Am wanting to convert to standard spring coils and shocks but cannot find an estimate on here. Seems pretty expensive estimate from repair shop for the conversion and just trying to find out if they’re in line with general estimate. Thank you

What makes this problem better or worse?

Rear suspension bottomed out

How long has your 2003 GMC Envoy had this problem?

A week