Casement windows are easier for the home handyman or woman to refurbish than sashes unless they have damaged iron frames.
Wooden casement windows can be repaired in the same way as sashes. A full refurbishment will include stripping all the paint, treating any rot, replacing damaged wood, and refurbishing fittings.
Use the guidance for sash windows; if the damage is minor, perform a basic renovation. If more major, go for a full renovation.