External-Cd drive or Replacment ?

Hey, I have the old UJ-857 in my mac.
So I either replace it with the new GSA-S10N or buy an external.

But if i needed to wipe the macbook clean or reinstall the software would I be able to select the external dvd drive like in the start up like i would if the superdrive worked ?

Why not start by chosing a back up plan, have a look at my comments and link here;
http://www.mac-forums.com/forums/os-x-operating-system/188880-iphoto-library-backup.html