How do I mass convert all my videos in iTunes From FLV to MP4?!!

My problem is a simple one that YOU will, sooner or later, face---else you already faced it. It is the DREADED mixed media from You Tube. HOW DO I MASS CONVERT MY ITUNES FLV VIDEOS TO MP4 VIDEOS. If MP4 will play Video & Audio---why do I need FLV files?

1. I have an old APLINE IDA-X001 Digital Automobile Receiver that I have ported my iPOD Classic to via their Alpine Proprietary High Speed USB2 Cable.

2. I have 800+ You Tube music videos from the 80s (what can I say, WE ARE ALL ENTOMBED IN THE MUSIC OF OUR YOUTH and I am a couple of months older than Steve Jobs---Double Nickel or should I say YEAR ZERO of our lord Rock & Roll!!!). When driving, I just want to hear the Audio Files from my iPOD.

3. 90% of said You Tube videos are in Flash Video (FLV), 10% are MP4.

4. You can only play FLV on outputs that have videos, MP4 videos can play in video mode else audio only mode---THEREFORE I NEED TO CONVERT all my FLVs to MP4s on my iPOD Classic (160GB).

5. Yes, there are a handful of FREE Video Converter programs out there and the one I have AV8 will convert FLV to MP4 one file at a time...drip,drip,drip!!!

6. I have 800+ Music Videos---I will have died from old age before my iPod is filled.

7. My DESIRED END STATE is to flip a software switch and have all my iPOD FLV videos magically convert to MP4

8. You Tube Download Modality: I find a song I like and Download it to RealPlayer. Once downloaded, I PAINFULLY convert it to Ipod (can't do more than 9 songs at a time). Once in iTunes, I sync it to my iPOD classic and bam---my videos are in my my iPOD.

9. Currently, the only songs that play on my iPOD are those I've purchased from iTunes.

10. Whudda I Do? The Apple Tech guys haven't a clue. Also. If I can only do it manually (I've got movies mixed in as well), how do I set up an MP4 folder and then only transfer that folder on to my iPOD?!!!