I prefer to cut the lines at each end, close to the fitting with diagonal pliers. Remove old line from retainers. Remove the fittings with a socket wrench. Remove the remaining piece of line from the fittings. Install new line, cut to length, into the fittings, flare tighten with a flare nut wrench, and secure into the retainers. Bleed the air from the system and fill to level. Drive on!

 

I am talking about the front brake lines. Exactly how can these lines be cut since there's very little space underneath the front of the vehicle?

 

Cut at each end(at the fittings) remove the old line and install new. Maybe you should leave it to the pro's?
Check out this diyer: