Hello.  I have a question about drywall installation.  My house was built in the 1960’s and the walls are covered with what appears to be 3/8″ drywall followed by 1/2″ of some type of plaster board.  So the wall covering is a total of 7/8″ thick, give or take.  I am wanting to tear down this old wall covering in several rooms and install 1/2″ drywall.  My question pertains to the door casings and finished wall thickness.  As I mentioned, the current wall covering is about 7/8″ thick.  New drywall will obviously be only 1/2″ thick.  How will this affect the re-installation of the door casings and what can I do if the wall covering thickness difference creates a problem?

Thanks for your help!