IF the key is worn down then the cyl is too, try redusing the size of you key ring.
it is not that hard to change the cly out, the tool you need are a stearing wheel puller, and a lock plate compressor, and some snap ring pliers.
these are all cheap tool might as well buy them when you get your new cly, Also a 4 way puller will work for removing the wheel too, and can be more usefull down the road.
after removing the lock plate there will be the signall switch blocking your way, remove the 3 philips screw and move it out of your way, you should be able to see the torx screw that holds in the cly, undo that ( a long handeled screw driver would work best) the cly should slide right out, and you can slide the new one right in
dave