Good to know about the Amazon thing. I had been planning on buying one in a couple of months-I'll definitely pick it up from there.
Two things I've been reading: the RAM *is* user-swappable, but Apple certainly doesn't make it easy. Opening the case does NOT void the warranty. I've also heard stories of Apple Store's Mac Geniuses claiming that if you buy the RAM elsewhere and bring it in, they'll install it free, but I highly doubt that.
I don't think Macs have had line-in jacks for a while now. I know the G4 that I have at the office doesn't, and neither did the Blue and White G3 I had before that.
"It's the four pillars of the male heterosexual psyche. We like naked women, stockings, lesbians, and Sean Connery best as James Bond because that is what being a [man] is." -Jack Davenport, Coupling
First thing I'd do is check all of the cables inside the chassis - make sure nothing came loose or is partially detached. I'd even reset the cable to the hard drive. Next, try to boot up from the CD Rom drive, but don't install anything.