Answer to: How do I fix my volume on my iPod?If you have a device that was manufactured for the EU market, you may be able to fix this with software called goPod. I have not tried this myself, but it is well-reviewed. You could also look into an in-line amplifier, which doesn't require any modification of the iPod itself. Finally, be sure to check that you don't have Volume Limit set on the iPod - you can set it using the iPod's menus. If it is set, the volume may appear to be fully up, but is actually being limited by this Parental Control setting.
Answer to: does battery replacement lose every thing on iPhone?The iPhone memory is non-volatile flash, which means that you won't lose data by disconnecting (or completely draining) the battery. However, you should *still* do a full backup before attempting any repair or sending in a device for service. For non-jailbreak iPhones, the iTunes backup is very complete. For jailbreak phones, install AppBackup from Cydia and follow its backup instructions, then backup using iTunes. If you need to restore, you'd have to re-jailbreak, install AppBackup, restore from iTunes, then restore your jailbreak apps using AppBackup's restore features.