Existing paint, adhesive and fasteners affect how the old surround can be removed. Some surrounding making-good may be needed. The service should not promise damage-free removal from every finish, and any unexpected deterioration needs discussion before the opening is covered again.
The decorative material needs sound ordinary support and appropriate fixings. Hidden services and uncertain substrate must be considered before attachment. This task excludes structural reinforcement and should not be used to stabilise an unsound frame through decorative trim.
Measure both sides and the top and identify whether one face or both are included. A doorway may have different trim on each side. The quote should describe the actual surround instead of assuming one opening means every adjacent decorative surface.
Replace the accepted ordinary decorative surround with suitable joints and fixings, leaving the agreed preparation for finishing. Scope limits: Ordinary decorative surrounds only. No structural jamb or opening modifications, specialist glazing, fire-door certification or hazardous-material disturbance.