Let the drive acclimate to temperature changes to avoid condensation. The temperature change may cause some condensation inside your hard drive. Acclimation times increase with greater temperature differences. While I've never lost data due to condensation, this recommendation comes straight from the manufacturer's packaging. Send your laptop through the x-ray machine, not the metal detector.
Many people are wary of putting a laptop through the x-ray machine at airport security stations.
In fact, the low level radiation emitted by the x-ray machine is less harmful than the metal detector you might otherwise bring it through. If you're really paranoid, you can have it hand checked. I've sent my current laptop through about 50 x-ray machines in the last two years and haven't lost a single byte of data on my hard drive. Backup important files. Carry original CDs for reinstallation.