I don't know about the800, but with the 900 and 3X, Page Menu always refers to the drop arrow in the upper right corner of the display and that is where we find the overdub or overwrite selection. This also only works when you select the multitrack sequencer record mode.
Check the step by step procedure on page 195.
Hope this helps.
Edited by billyhank (01/09/14 01:02 PM)