Do not worry about step 4 unless you do not have a spare. Just put the new tube in & worry about trying to patch the one that was punctured later.

Also check the rim for the cause of the puncture as well. Sometimes a spoke can punch through rim tape, there could be something that was caught between the rim tape & the tube that caused the puncture, and if the rim tape is worn just the rubbing between the tube & bare rim/spoke ends can cause a puncture.

You only need to take half the tire off the rim. Also do not "run" the tire levers around the tire between the bead & rim to seperate it from the rim. This can damage the bead. Use the levers just as they were designed, as levers. After the first 2 or 3 only one lever is needed to "pry" the half tire off the rim.