consider replacement instead with the newer cement board which will not
allow mold growth like the plasterboard does in its paper covering.
behind those damaged walls lies the unknown mold growth and hidden
pipes and wiring. this is where an estimate may wind up with add-ons.
in buffalo ny you would be thrilled to find a good carpenter at $250
per 8-hour day labor plus all parts. expect to pay more than this if
you haven't known the carpenter for 20 years or if parts or labor are
in short supply. subject to your family needs, i would predict the
longer you can wait the cheaper the labor will be as the repairs get
caught up in your area.
home depot or lowe's can deliver what materials you need. or they can
do all the work.
i know it may not have been in the original house plan, but it is a
great opportunity to add see thru fireplaces, french doors,
room-to-room windows, etc. and make your home more inviting.
Doing just the lower 4' could be problematic. If the original plaster
thickness isn't the same as your drywall thickness then shimming will
be required. this would add time and labor expense. May be cheaper to
do entire wall. Materials are cheap relative to labor. I good drywall
crew could do an entire room in less time than it would take them to
marry the new and old and make it look right. No price estimates per
say but around here independent drywall finishers start at $35/hour
plus materials. (PA)