Search:

"S" в названиях смартфонов обычно означает 19-ю букву латинского алфавита
также добавляет +1 к карме айфона :)

Select all mp3 files which you want to get size of
right mouse click
If you on Mac, select Get Info
If you on Windows, select Properties
I hope you are not on Linux, because I might need to look...

I've done it for iPod nano
I don't use m4b and AKAIK iPod can work with mp3 audiobooks and remember the bookmarks
You'll definitely need iTunes to create audiobook for iPod