First of all, yes you can install install Ubuntu without having to loose Windows or any of its DATA's only if you're installing to a separate/clean partition where Windows is not installed. Generally, Installing Ubuntu will only replace the GRUB (which is the boot loader for Linux) though it won't harm if you follow proper process. There are two methods to install Ubuntu, which are;
- Install inside windows using Wubi (Unfortunately its not compatible with Win 8 & does not support 13.10)
- Install onto a separate partition (I personally & most users would recommended this)
Assuming I've answered to the point 1;
I found this article about SwitchingToUbuntu/FromWindows/TransferringFilesAndSettings, which may interest you on how to transfer your files as in your point 2.
Libre Office is better but not like MS Office. Here's a comparison between both. In any case, you need MS Office within Ubuntu, you may also achieve this by using wine, an application to run windows compatible programs within Ubuntu. Installation predeceases can be found by searching here within this community.
Hope this clears all your questions which is asked. Feel free to comment if there's anymore needs to be clarified.