The computer you are replacing is still functioning, correct? Is there a reason you don't want to use
Migration Assistant?
What "router" are you replacing? Does it
not have an app to view its settings, like an Apple router does (
Airport Utility [image below])? You'll probably want to see all that info and write it down, anyway, whether you or the "tech" puts it in the replacement. Of course, you should also have all that info in a password manager, also.
No reason to let a stranger, with unknown health problems, into your home. Your Mac already has the capability to transfer all your stuff for free.
As they say on NPR/PBS; "Let [your Mac] do one more thing before you get rid of it!"