The replay files are just instructions that only Prologue can understand. It's not a video file. You need to use some sort of video capture device to record your replays and upload them to youtube.
But somehow it can be done. Look at some replays at YouTube. There is another GT site were some guys do it. I doubt it if someone here doesn't know how. probably with some kind of conversion program.
Capturing the PS3's video output is the only way to go.
Without a Debugging Station or some "special" device you're limited to analog output because the PS3 is alwys using HDCP.
No, there is no conversion program. Prologue is the only program that knows how to use the replay files. The only way to make videos is through capturing the video being played by the PS3 and Prologue.
It's slightly drastic, but for quality it's the best way to go. You can also look at getting a Dazzle DVC 100 for less than $100. The two main drawbacks to using something like a Dazzle A) its standard definition and B) you have to constantly change the PS3 output to 480p before you record : / HTH.