I have a pre-devalue ticket fron NY-Europe UA-LH-LH-UA in business.
I tried playing around to see what changes can be made w/o triggering reprice.
I can make virtually any change w/o reprice to new chart. i.e NY-TLV LH w/date change, only 10K more per leg.
LAX-Europe no additional. NY-NRT UA-ANA only 10K more. NY-Europe LH-LH change to First, only 17.5K more.
(they do charge $100 change fee)