5 - 30 minutos
Battery getting on a bit
Relatively easy to install
back cover comes off easily after removing the 2 screws,
removing the battery connector is a little fiddly but with a little patience the job was done in about 15 minutes.
Mine also had a large amount of glue applied to the battery so it took a little longer to remove.
take your time
There doesn't actually seem to be any reason for Apple not making the battery user replaceable apart from wanting people to pay them more money.