Have done that many times, isolate a conduit, hook welder leads at each end. Hook a air compressor on one end and stand back. When she blows you know you can pull out the bad and in with the new.
I have also used tubing and steam. Force the tubing up the conduit with steam coming out and you can break up a small iced in area.Blow it out and pull in new wires [Linked Image]