1991 Nissan Sentra Leaking fuel line

Depends on where it's leaking and how your going to route it and the material you use. You need to see where your going to be able to splice into, if there is areas that are stable enough to hold up.

Are you going to use high pressure fuel hose? Or steel line with comprssion fittings?

Factors that can turn this into a nightmare are "what else will be disturbed while doing this? PRimarily brake lines. IF the lines are run close together, moving one line cause disturb another and cause another leak.

Can a BY mech do it? Depends on the one doing it.