Even without owning an iPod, I would still use iTunes for your music (my preference only).
The program is free from Apple and easy to setup.
Once it's setup, all you do is insert your CD into the computer and iTunes asks if you want to import that CD. You can pick what sample rate for MP3. If disk space is not an issue, I would go with the highest MP3 sample rate they offer, or not less than 192.
Once you have the songs into iTunes, you can make Playlists that you just drag your songs into. You can have as many playlists as you like.
Then from the open play list, you can burn a CD with that playlist group of songs on it.
Keep in mind that MP3 is a lot smaller file size that straight WAV type files.
I have over 300 playlists. I have one that's Motown. In that playlist if have about 130 songs. All of those songs will fit on one CD in MP3 format.
In my case I have a '09 SERG with the HK head unit and I usually use my iPod through the AUX input, but from time to time I do the MP3 CD's for a day or two.
If you burn the playlist to a CD, you could than download that CD content into the Garmin or copy them back out to another folder on your hard drive.
It sounds complicated, but it really isn't.
I have over 85k songs in my iTunes right now and it's very easy to navigate through them.
Good luck and I'm sure others may have a better idea for you. Also, I'm not familiar with the Garmin and maybe they have their own software for this purpose.