Its usually possible to put new lenses into an old frame still in very good condition, but there is a risk that the frame will break or be weakened or the lenses not fit perfectly ( depending on the type quality and age of frame). I think this is why its not done as much now. I was told it would be at my own risk if I reused an older metal frame so decided on a new one, (and keep my previous one as a back up pair) but have reused frames in the past. I had one pair ( a metal frame) where one of the replaced lenses didn't fit quite perfectly and fell out sometimes - a risk I was warned about.
The other issue is that the 'old' spectacles usually need to be taken away for a few days to have the new lenses cut and fitted. If the lenses are anything other than very simple, the lenses may need to be ordered and made specially to prescription to await the frame. So if your lovely frame is your only usable pair of spectacles it can be quite inconvenient to be without them. An on site spectacle glazing facility may make this easier.
I would ask the dispensing optician for their advice.