Good question, I can speak to part of this, I have had the same Maxtor 8.4 gig drive in my truck for 3 years. I live in Denver Colorado, the temp swings can be sunny and warm in the day to below freezing at night.
I have had no trouble at all. The player is a comercial unit mounted in a compartment underneath the jump seats in my toyota truck. No padding or insulation was used, infact It is not "mounted" just placed in the compartment.
Hope that helps.