This was probably beyond my skill level, but I tried this and it seemed straightforward, but after re-assembly, when I hooked it up to the charge cable, the watch doesn't seem to be charging and won't turn on.

This is a great guide! IMO the hardest part is getting the battery connector on the new battery in place. The plastic connecting the battery connector to the battery has to be very carefully folded and tucked between the battery and the pressure contact, all while keeping the pressure contact in the right place. (Use the old battery as a guide) Anyways, overall an awesome guide and very happy with the kit!