Since you are new to Linux, I recommend you download and burn a rescue CD/DVD like SystemRescueCD (see www.distrowatch.com
) before you do anything further. If you happen to mistype and reboot, you'll have to do a lot of re-installs otherwise.
I also recommend you run the commands people are telling you by prepending them with sudo - examples
[hh@mybox ~]$ sudo ls /boot
[hh@mybox ~]$ sudo fdisk -l
Please provide the output to the following:
[hh@mybox ~]$ sudo grub --version