If you have a long email and only want to reply to or forward a specific section, there is no need to include the whole message. Highlight the section you wish to reply to or forward, the iPad pulls out just that section for the new email.
If you make a mistake whilst typing, shake your ipad and an 'undo typing' option will pop up. If you feel uncomfortable shaking your ipad then there is an undo button on the .?123 on the keyboard and a redo button on the#+= keyboard.