It's a Samsung TS-L633 drive in those...
this should be compatible.
http://www.pcworld.co...ive-04888796-pdt.html
I'm not familiar with that model to know exactly how the drive is removed, but it's not normally too hard on most laptops, normally you'd have to remove a couple of rails from the side of the old drive to fit onto the new drive but they are pretty standard under the extra bits they screw to the side.
An external is an option if you don't want to try changing the drive and having to plug a extra lead in whenever you want to use it. (though if you get a small laptop drive based external CD drive there is a good chance you might be able to remove the drive from the external case and fit it to the laptop at a later date)