Not really.
Depends on the model
Call Colt.
You will have to call Colt with the sn to find out.
DPMS sell a complete kit for $68.
about 1978
IT IS A 1957 MODEL OF THE COLT DETECTIVES SPEC .38
yes
made by Colt in 1918. not unusual to see a springfield slide on a Colt frame
The extension tube of the commercial buttstock is actually thicker than the milspec extension tube, and they tend to be slightly angled at the end.
Would need serial number to answer or look it up at proofhouse.com
Don't know price , but produced in 1970
Depending on what "very good" really is, 20-400 USD