There is no need to change the new drywall. Your wall surface process is intact, just not yet finished in regard to the window trims and jamb extensions. You need to add jamb extensions to your window and door jambs to make them thicker. This is standard trim carpentry stuff.

All the window and door casing trims are to be carefully removed, nails removed from the back of the trim to avoid damage to the trim face, and the existing trims saved for re-use. Then the window and door jambs must be extended and custom trimmed to allow the casing to re-install correctly over the face of your new drywall.

The jambs must be extended by adding a piece of wood trim thick enough to extend the wood jamb to a depth allowing the trim installation. We at Mosby Building Arts sometimes use a parting stop wood trim which is ½” x ¾” to extend the jamb equal to the new drywall thickness of ½”. Often times these wood trims must be custom ripped on a table saw to a consistent width that matches the depth of jamb extension required.

These trims get installed with a 1/8” reveal which means set back showing a 1/8” inch shoulder or corner of the existing jamb wood. The carpentry trim rule is to generally use a reveal on the job-site on all trim applications. Flush or perfect alignment of wood trims is left to the wood shop where the tools and clamps are more controllable. On-site trim carpentry involves leaving a reveal between the existing wood jamb and the new applied jamb extension trim. This trim gets installed with finish nails that are set below the surface of the new trim. Trimming in place of the new applied jamb extension trim may be required by either a wood plane or a belt sander with the carpenter taking special care to keep the drywall undamaged.

Then re-install your casing back over the jamb extension wood trim, fills nail holes, and paint to the finish desired. I warn you that sometimes these old window and door casing trims do not remove successfully from the windows and doors. Our experience is that about 30% of the existing trims split and need replacement during this removal process which requires having a mill shop custom make the new trims. This brings up the question of replacing all the trims with new, custom made to exact profiles casings.