You are probably looking for the 140A fusible link on the positive terminal. It is the one closest to the battery post (on top, rather than on the side of the battery).
While at it, I'd also pull the fuse #36 in the picture below. That fusebox is also by the battery.
Now that I have answered your question exactly how I thought you asked, I will give you my opinion.
Option #3. Disconnect the negative battery and minimize all the risk, not only to you but to other electrical components.
Personally, if I were a client and my mechanic told me that they accomplished an electrical repair and I still have my radio stations & memory driver positions intact, I'd be very happy. That's going above and beyond.
However, if he/she told me that they intended to save my memory settings, but due to an abundance of caution and a concern for safety they were unable to do it, I would be more than elated that it turned out like that.
Assuming the alternator is completely dead, that means the battery has died at least once and the memory(s) that you are trying to save has/have been re-stored before. It's not that difficult.