Can anyone give me a rough idea of how tricky it is to replace the DVD drive in an AlBook? The combo drive in mine is broken (mangled a DVD I put in there and won't accept any others after that). PowerBookMedic.com said they could fix it for about $300, but that's steep enough that I'd like to do it myself if possible. The thing is more than a year old and I didn't bother to get AppleCare, so no warranty to be voided.