Copy and paste is very easy but slightly limited. You can only copy and paste from the browser, text messages and from text entry fields. For example, if you want to copy a text message, long press on the message and select copy, it will copy the entire message, however. From the browser, hit menu and select text, then drag your finger across the text you want to copy. Copying from emails is not possible at this time, the gmail app does not allow it.
2. Correcting a typo is 100 times easier than the iphone, just tap approx where you need to correct and use the trackball (which is very easy to reach in portrait or landscape) and move the cursor.