Well, if they kept the sound effects to a minimum you should get quite a good amount of compression. The spoken word is like that in MP3 format. So let's say that you have 600Mb on a CD and that compresses to 200MB. Now if you have a good amount of RAM in your system, you can cut and paste into whatever audio editor you use.
Disclaimer:
I have never tried that with such a large file but I have used a few different proggies to cut and paste bits together for my answering machine. And if I read you right, you are going to end up with one huge file that may not work in your car due to limited resources.