Editing grub is dangerous
Please explain.
My input here is, that as long as you know what you're doing, it's not dangerous. Before editing the Grub, best is to save a backup copy in case things might turn to the wrong side. Booting up with a live cd/dvd and it's easy to replace the corrupted Grub with the old (back upped) Grub.
Be careful, can render your machine unable to boot.
This warning makes more sense.
I need a grub editor. I saw a sudo command that was supposed to do it but gedit was not found.
Editing the grub file didn't work.
Before doing anything stupid, what do you want to edit exactly? What command did you saw? Were did you saw it? Provide us with more info please and, if possible, a link to a website you saw that sudo command.
And beside the above, sudo is a terminal input, not a Grub input. In a terminal when you want to run a command which need root, you type sudo first and then the command you want to run. Sudo has nothing to do with Grub. But first provide us with answers on the above questions .