Will colostomy significantly change my lifestyle forever?

Takes time to adjust. It is a major shift in life and takes tremendous courage and tolerance. It is a shift in thinking. Dr.Remen has one she speaks about her life her website http://www.Rachelremen.Com/ktw.Html i was inspired by dr. Remen you might be able to connect with her regarding coping.
Yes. But with time and experience you should be able to continue to live a full life. Ask the ostomy nurse for literature on people with colostomies that are in the public eye - i think you'll be pleasantly surprised.