Not a lawyer or DNA but...
They will most likely say you voided your warranty b/c a ducati certified tech didn't do the work (techs at my local dealer are too dumb to even flunk the certification test). But it really depends on how cool your dealer is. But if you can prove the work you did, did not cause the problem legally they can not void your warranty. So if the frame cracked and you had done you 600 m inspection legally you are straight, but that doesn't mean they won't try to screw you.

Just do a google search for 'Magnuson-Moss Act'. There is days and days of legal jargon to have fun with re. warranty disputes/issues.