First of all there is no such thing as a button text. It is either part of the background video (even if menu is still - it is one frame video) or specialy done subpictures (also an image). As it is not a text - you ca't easily edit it.
By your description it looks like you have a second (actually quite rare case). It is possible to edit subpictures and then put edited one back, but it is not that easy.
There is quite easy procedure to get rid of "button text" in case it is part of the menu background:
1. Import disk into DvdReMake Pro;
2. Save menu background as a bitmap (right-click in preview and select "Export frame"). It is a motion menu - choose the frame you like most as at the end of this procedure you will convert your menu to still;
3. Open saved bitmap in any editor and get rid of the "button text" in any way you like - blur, strike, etc
4. Download muxman (http://www.mpucoder.com) and author a dummy DVD with edited bitmap
5. Import this dummy DVD into DvdReMake Pro;
6. Open your original menu in preview, right click and "replace with still" (DvdReMake Pro 3.1+ is required).
7. Select block with your edited bitmap
That is it. Now you have menu with new background.