Welcome to LQ.
1) To change the date manually you can use the date command - see:
If you want to syncronise with an ntp server then:
2) There are many distro specific ways to do this - perhaps you could let us know what you are using and perhaps enter the information into your profile.
3) Any modem should work so long as it is a pure hardware modem.
4) What medium are you trying to backup to?
5) I tend not to read books - just LQ and google. For a good list of howtos see:
The LQ Wiki: http://wiki.linuxquestions.org
The Linux Documentation Project: http://www.tldp.org