Well, I went kinda nuts and bought one these units after reading all about them for many days

Not nuts at all. They're cool. Still the best MP3 car player available, after all these years. Congrats on your new toy.

Others have already commented on the FAQ, but I'll go through your posts and point out specific FAQ entries that relate to your questions, just so you have the easy links at your fingertips.

Should I immediately do a firmware/software upgrade on this unit prior to loading any of my CDs?

Yes. Install the version 2.0 final, developer, of the firmware, and version 2.0 final of the empeg software. Detailed instructions and tips are found here. If you are using USB as the connection to your PC, make sure to read this.

Since I want to use the RioCar in my car and in my primary home rack, I'd like to use the best sounding, within reason, format as possible. Should I use wav, 320kb MP3, or somehting else?

MP3 creation is discussed at length here. But really, the most important thing to remember is that tagging and organization is just as important as audio quality, click here and here for more info.

Also, I usually use EAC for my CD copies. What software should I use to rip my CDs for copying to the RiaCar?

EAC is great, continue using it. Make sure you've got the latest version of the LAME encoder to go with it.

Are you saying that Rio still makes and sells a dash mounted and moveable music server?

Nope, the RioCar was it.

I'm currently planning on using 320kb VBR MP3s unless I change my mind or get convinced otherwise. I think that even at this high bitrate I still should be able to fit quite a few albums into the 60Gb of HD space.

Keep in mind that the hard disks can be upgraded.