This one is easy to answer.
Replace every line and hose that is leaking, worn, or suspected of either.
With relatively new cars you can clamp the fuel line so you don’t have to empty the tank. Since your lines are 15 years old I would replace them so clamping is not a good option.
First empty the tank as much as possible (driving and/or siphoning).
Then drain the rest by cutting the fuel line/hose to the filter and drain the remaining fuel in a container. After 15 years it is usually not possible to that the lines/hoses of without severely damaging them. Draining the tank by taking the hose of may very well result is a lot of gasoline in you sleeve.
If you can’t remove the fuel line after cutting/damaging it you have a problem, since your car won’t run. Although being a rather experienced wrencher I left this job (on a 300SE 126) to a Mercedes specialized and trained Indy. A decision I never regretted (he did).