2013 macbook pro battery replacement successful
original battery in bad condition
It worked. I was being ultra-slow and careful. If you're good, this could be done in 45 minutes. With help, maybe 25 minutes.
I did not do the scary "take your whole laptop apart" method shown on ifixit. Instead used the youtube "cut the battery glue with string" method. https://www.youtube.com/watch?v=DPqrmt-I... . Took 20 minutes to figure out what to use -- it needs to be thin / non-metallic (Li-ion battery!) / fairly tough / and have some tensile strength -- I used non-milspec 90 weight paracord with the core removed. Floss didn't work. Heavy string could have worked if I was willing to replace it for each of the 6 batteries. I attached the paracord to old chopsticks to allow me to pull hard without hurting my hands. breaking the chopsticks in half would be made it easier.
Discharged the batteries completely. Opened the case. strapped the laptop to something so I could pull hard on the paracord.
Once the batteries were out, I didn't know whether I needed to get the difficult-to-remove glue remnants off the macbook case before sticking the new batteries in. My concern was whether close contact with the case was needed to keep the batteries cool. I couldn't find anything addressing this question -- and I didn't order the ifixit glue dissolver with the battery -- and so I left it alone. I just positioned the new battery so it aligned with the screws, marked the edges with a marker, peeled the adhesive coverings off (the ifixit battery has adhesive strips on the bottom of the batteries) and stuck the batteries in.
If you want to get the glue out, go ahead and spend the extra money at ifixit to get the glue dissolver along with the battery, even if you are using the string method. Apparently ifixit had to work pretty hard to find the right combination of solvents to dissolve the stuff.
It's been a week. Seems to work fine so far. So I'm pretty happy. Thanks ifixit and everyone.