As long as you have room to do it, CA hinges are by far the easiest, BUT you cannot put the new hinge where the old hinge was, you'll have to cut a new slot next to the old one.

For more on installing CA Hinges, read this:

[link=http://www.rcuniverse.com/magazine/article_display.cfm?article_id=55]Installing CA Hinges[/link]