Originally Posted by erik123
Actually - I would like to change the ams-nyc (on KL) to BCN-NYC on Co. My main question is whther I would likely lose the seats on the outbound (NYC-AMS) if I have them reissue the ticket.
So long as you're not manipulating that outbound sector in any way (e.g., turning it into a connection), those seats are safe. They'll drop just the return, and book the BCN-EWR flight for you. The ticket will have to be reissued, though that shouldn't be a concern.
Worth pointing out that awards do allow a stopover. So if you would like to add that flight AMS-BCN to your ticket somehwere in your trip, it won't cost you any more miles.