15 minutes - 1 hour
After 7 years our battery wasn't holding a charge more than a few minutes. A new battery and tools was only $15 so why not revive it? (I already had a T6 screwdriver from a previous hard drive replacement.)
Kit came quick, and as soon as I had time, I replaced the battery. It took maybe half an hour, probably less. Instructions were clear, and the advice at the bottom helpful. No problems opening the case. The old battery was hard to remove, as described, but using the tools provided, I was able to work it free and install the new one.
When opening the case, I gave up on using both tools. Sliding the large tool all the way around the case did the trick, and using two tools didn't work for me. The big one kept falling out when I tried to insert the little one. If I had another hand, two tools might have worked better. I did use the small tool to get under the old battery from different sides and pull up a little to release the glue. Didn't see an answer on what glue to use to install the new battery, so I just put it in, hoping that a) it won't move much anyway in that tight space or b) it will stick to the old glue. The only other trouble I had was getting the headphone connector back in. It was a little tricky to get aligned right, but just took patience.