Shouldn't the dentist replace crowns after root canal as part of procedure? My dentist would not put the crown he removed from my teeth to do a root canal unless I paid $600.00. He said my insurance did not cover it. If that is true, sould he have told me

Confused. A root canal and a crown are 2 separate procedures. And always 2 separate fees. I don't fully understand your question. Did you have an existing crown on the tooth. If so, existing crows sometimes need replacing and always at an additional fee. If you did not have an existing crown and need a crown, then the crown is an additional and separate fee. Have your dentist discuss this w you!
The. The crown was probably removed since there was decay under it. That was the reason you probably needed to have root canal therapy on that tooth. If that was the case, it would have been best to explain to you before treatment commenced all of the procedures involved and the associated fees. Your dentist cannot recement a crown that doesn't fit correctly. If the tooth needs a new, well fitting crown, then you will need to do it to restore the tooth correctly.
Procedure driven. Dentistry is a procedure driven profression. Also, there are many unknown variables in this case so it best thing to do is to visit your dentist and have a rational conversation about your concerns. I am sure you and he can come to a rational and fair agreement.