Usually easy, but fiddly. You need to push the clips out of their holes to remove the cable. Remove plastic inner fender liner to access the part of the cable that runs through there.
A tip: Tie a string to the end of the old cable before you pull it through the rad support into the fender well. Undo it and tie it to the end of the new one. This will make it easier to pull the new cable back through the rad support to the latch.
What happened? Did it pull through at the release handle, or did it break in the middle somewhere?