A lot of times if you just wait a little bit, it will spit the disc out on its own if it can't read it. If that doesn't work, the drive's probably gone bad, and the problem with slot loading drives like Apple loves to use, is that you can't use the paperclip trick.
Not sure why you have to wait until monday to call, since AppleCare reps should be available pretty much 24/7, and could probably schedule an appointment at a nearby AASP or retail store. Of course unless they have a drive in stock, you're looking at Tuesday as the absolute earliest to get this repaired. The replacement drive wouldn't ship out until at least monday, then assuming everything goes as expected, they'd get it tuesday, put it in, test it a little, and then tell you to come pick it up. Just make sure that when you check the unit in, you TELL THEM that there is a disc in the drive. If the tech who works on your system is anything like me, they're overworked and will not check the drive for anything left in it unless there's a reason to. Once FedEx picks up the old drive to be sent off to Apple's receiving warehouse, that's it, you're not going to get that disc back. When I left work on Friday afternoon, I think I had something like 25 customer units on my shelves, and 2-3 more in the incoming cart. On a good day, I can do maybe 5-6 units, and apparently that's way above the average. So if for some reason your system came to me, it might be 4-5 days before I even get a chance to look at it. Be prepared for the possibility it may take longer.
Holding down the mouse button while restarting no longer works in Snow Leopard. Help! I didn't know the advance CD I inserted doesn't yet exist as far as GraceNote knows...
And can't call AppleCare till Monday...

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