the ultimate noob here

[Willin08]

A custom pack as it says, is a package of configurations for your phone. For example, all branded phones come with certain menus and icons from the network (like T-Mobile or AT&T).

If you want to get rid of it, you must flash your phone to a generic version.

You can put acoustics and camdrivers to your phone if there is any for it. For W580 there are a lot of modding you can do.

Here you have an acoustic file.
DB2020 Acoustics - Official Topic - Top Sony Forums

Here are some camdrivers:
W580I camera - Top Sony Forums

To upload them you can follow the tutorials or guides for tools like setool2lite or XS++

Other guides here:
Tutorials Guides - Top Sony Forums