The optical drive can be replaced as long as you find a replacement one specifically for the Asus F5RL laptop. Click the following link for a Youtube video that demonstrates how it is done. Note, the video (which has no audio) completely takes apart the laptop, but you do not have to go to that extreme.
You just need to unscrew the main underside panel (starting at 0:16 to 0:32). There is a single screw that secures the optical drive in place and is found next to the fan. Skip to 1:50 which shows you how to remove the optical drive. Simply remove the screw and pull the drive out. Naturally just do those steps in reverse to install the replacement optical drive and secure the underside panel back to the laptop.http://www.youtube.com/watch?v=Uk8qFczG-5E
You can purchase a replacement optical drive from the following site or Google around for a better deal:http://www.super-laptop-parts.com/asus-f5rl-series-tsl633-dvd%C2%B1rw-burner-drive-8-x-slim-p-9539.html