Reboot?
ZAP PRAM (Apple + Option + P + R at the first startup chime)

That covers it for right now, try those and see what happens.

I recently had to replace a Slot Loading DVD player in one of these, it too, just died on me.
Fortunately, the replacement, purchased on eBay was quite cheap. They are easily within the scope of anyone with a little dexterity with a Phillips screwdriver, to install

P