How do you install a skimmer in an in-ground pool that is 20 years old?

First of all you cut the concrete 2 paralell cuts from pool edge toward the pool equipment, jack hammer out concrete remove old skimmer and coping , plaster, etc, trench out from skimmer location to exist skimmer/drain line,set new skimmer in place plumbin to old skimmer line pour concrete around base of skimmer to set in place, wrap 1/2" rebar drilled and epoxyed into exist pool gunite, build form around skimmer and rebar, pour form with rapid set mortar, pour final layer of finish concrete, replace coping repair plaster and voila you r done