So I'm planning to buy my father a new Kindle for Christmas. We've discussed it and he doesn't want me to spend too much (despite the fact that I can afford it and want to but whatever

)
Anyway as a nod to his concern over cost I'm thinking of getting a Paperwhite with Special Offers but I have a couple of questions:
1) How intrusive are the ads? AIUI it's mostly screensavers is that right? My concern over this is mainly whether it will interrupt the flow of navigation on the device. Dad's approach to computers and tech things is to learn a series of actions by rote (he's got little scraps of paper with things like how to program the DVR, some are laminated!) and if the ads throw the sequence off it'll make it harder.
2) Does the fact that he has no Wifi (no internet at all) make a difference? Will he be stuck with the same ad all the time? Will it nag him to connect?
3) Is the removal of SO tied to an account or the device or both?
Thanks