~snip~
once I've checked that all this works I might upgrade the current ledger as well. am I being too cautious?
It would be good if you check which firmware version you have on the Nano S, because such an old device probably has a firmware version that cannot be upgraded. Practically, it is a device that may be completely unusable because it cannot work with Ledger Live, and most likely not even with Electrum, not to mention outdated coin apps that would represent a security risk even if you could connect the device with some software.
I am not sure if you need the newest Ledger Live versions before being offered a firmware upgrade. I never tested it.
It is always recommended to have the latest Ledger Live before a firmware upgrade, and even if the OP tries with some older versions, he probably won't be able to upgrade a device with such old firmware. There is only one way to find out the answer to that question.