frame rust question

Hey everyone, obviously i am new here and im sorry if im not asking this in the right place. is it very hard hard to replace frame rails on a 67 barracuda? i found one for sale, pretty rough but very salvagable in my opinion. i have been around cars most of life, know a my way around cars but not very good at welding yet, was gonna learn on this car if i could. thanks all and sorry for the spelling!