A couple of GarageBand questions

Hi,

I've recently started doing a new radio show, and I'm planning to use GarageBand to pre-record the ones I won't be able to do live. Currently, I'm getting music in by simply copying and pasting the music file into the main GB project, so the hole song goes in as one track, is there a way of turning the volume down for certain parts of that track? For example, is there a way to turn the volume of that track down for the last 5 seconds of that track so the listeners can hear my voice over the outro? This would also be useful for music beds.

Also, is there a way of cutting the length of a track? Say I copied in a one minute bed, but I only talked over it for 30 seconds before starting the next track, how could I cut the remaining 30 seconds out?

This is using the latest version of GarageBand on a MacBook Air. I do have the older, more accessible version of GarageBand, but I'm upgrading my Mac soon so I might end up losing that.

Any help with how to do these on either versions is greatly appreciated.

Callum.