"RogerT" wrote in message
How much more difficult or complicated is it to go ahead and replace
the entire windows, frames and all...


If you ask me, that is the only way to do it. I've found many air
leaks in the surrounding frames. The old frames sometimes are not
"square". And old wood may not be totally sealed and will
expand/shrink with changes in humidity.

This is one thing where it is well worth any extra expense to replace
the entire window.