What lifestyle changes do you have to make if you get your colon removed?

Not many: While it is nice to have the whole colon, you can survive without it just fine. The colon absorbs water, so you may have more runny or liquid stools, but otherwise, you should not have any decrease in life span -- although it depends why it was removed? (for cancer: there is a risk of recurrence; for ibd, perhaps recurrence in the small bowel).