Hi Global,
Dell ships this system model with maximum of 6 GB DDR3 with 1600 MHz memory.
You may install Ubuntu if you wish to. However Dell will not support this software as Dell did not ship this system with Ubuntu.
Only way to restore the system back to Windows 8 is by recovery media or by manual reinstallation. Please find the link for instruction to create recovery media:
If the HDD is damaged, and if the system is within warranty, Dell will replace the HDD with the factory image. In case the system is out of warranty, software has to be installed using the recovery media.
The system is shipped with 32 GB mSATA drive. You may install the Operating system on the mSATA drive. However 32GB mSATA drive will not be sufficient to install other applications along with Operating system.