Excellent; I chose to replace with a 1TB SSD and the guide worked for me all the way through. This is the most ambitious fix so far for me and has given me more confidence (not to say a faster computer with doubled storage) so thank you Andrew.
It isn't necessary to remove the rim if all you are doing is changing the battery. That becomes necessary if you are to proceed farther into the phone.
It might be good to begin by saying switch the phone off. The Fairphone is for everybody and most will have no experience of disassembling electronic devices.