If the existing barrel is not an anti-snap sdesign, you may be ableto snap it (you may trash the handle escutcheon as well)
https://www.youtube.com/watch?v=TCufUpr_QRY
http://www.locksmiths.co.uk/about/public/cylinder-snapping/
http://www.londonlocksmith.co.uk/page/id/129
http://www.instructables.com/id/How-to-pick-a-common-cylinder-lock/
https://www.youtube.com/watch?v=D2Z0ZN9hvOw
https://www.youtube.com/watch?v=rHZZCEP5lPI
http://tradelocks.co.uk/domestic-locksmith-tools/signature-range-tools/nigel-tolley-plug-puller.html
Make sure your new cylinder is the right length inside and outside.
Or call a locksmith, August 2015