I want to disable the shortcut of shift and up arrow. I hit it by accident when reaching for the shift and it winds up deleting most of what I've already typed.
Does this combination remove the text? It should just highlight some of the text, and if you inadvertently type something when this happens you should be able to undo the changes by hitting command-Z.
One thing you can do is use the system's "Keyboard" system preferences to set it up to do a relatively benign task such as saving the document. To do this, go to the "Keyboard Shortcuts" section and choose "Application Shortcuts" in the list to the left. Then click the plus button, ensure either your word processing application is selected or "All Applications" is selected, and then type "Save" (no quotes) in the "Menu Title:" box. Then in the Keyboard Shortcut box press Shift-uparrow and that combination should appear. Save the shortcut by clicking "add" and you should be good to go. Now for the designated application the shortcut will not select items, but instead will invoke the "Save" command.
Keep in mind that this will replace any default commands, so in this example the normal "Command-S" for saving will be disabled.