Yes you can.
Remove the plastic surround from the bottom of the steering column, there are 2 or 3 screws holding it on from underneath. Unclip the wire going to the key reader. Looking at the right hand side of the barrel towards the bottom there is a hole, turn the key to "ON" and insert a pin (paper clip works) and the just pull the barrel out.
You can key the new barrel to the old one fairly easily, once you get the new barrel you will see how it is done. You will need to assemble the spring clip that holds the barrel in place as well. Pull the old barrel apart taking extra care to keep the brass slides in the correct order, these are numbered and you will need to fit the new slides in the same order.
It sounds harder than it is, once you see the new barrel and start pulling the old one apart, you will see how easy it actually is.