Is it difficult? Not really
Is it worth it? Probably not
Will I void warranty? Might do
Why should I bother? (other than for this back-up) Dunno.
Sorry 🙁 Just noticed the phone’s being collected tomorrow.
You won’t need to back up your apps as Google Play will retain your list of apps on-line (google play > menu > my apps) or something.
Your contacts should all be gmail contacts – just re-sync when you get the replacement phone.
Music and Photos should be on the SD card – or just transfer straight to PC as above.
Settings…. have you customised it significantly?
The only thing that may be of concern are your SMS messages. There’s an app for that.