Replacing nylon inline fuel supply line?

The easiest way to replace those lines is to get the line kit from the parts store, they generally will loan you the kit and you pay for the fittings and the line. What I do is go along the line and release all the line retainers first, then pick one end and disconnect it. Now take a cheap hose barb like from Home Depot or similar, cut the fitting off the end of the existing hose and connect it to the new line. Now disconnect the other end and start pulling on the line, you use the old line to help guide the new one into place. I have reused end fittings before by dipping the end into boiling water and working the old line off, but it takes a while to do. Once you have the line in place you select the correct fittings, then dunk the line into boiling water, pull it out of the water and push the fitting in until it is seated. Then install the line clamp. Now cut the line on the other end and repeat the fitting installation.
Do not try to slit the tubing to release the fittings, it is very easy to cut through it and make a slit on the fitting which will cause a fuel leak. There are a number of videos showing the process online.

You are welcome. We will be here if you need us.

I would cut the out the part that is leaking and use this repair kit,

https://amzn.to/3Mp4QE5

It 12 bucks and should help you fix the problem. Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.