The good news is that if you want to do this, the only work required is simple enough you could do it yourself and it will still look fine. If you do want to do you it yourself you need a few things.

-Adigitalman's Extended edition of Episode 3 (Can't supply you with this, but it sounds like you already have it)

-Some decent video editing software (Sony Vegas, Final Cut, Adobe Premier, etc.)

-A little bit of patience.

Basically you would have to take Adigitalman's version and open it up in the video editing software. It's then a simple matter of cutting out the footage you don't want and joining the ends together. Then just crossfade the audio and your good. Or, use your original copy of Episode III, and take the transition from there, so that you have all the original audio.

Once you have done that you would have to re-export the video (in other words save it as a single movie file), burn it to DVD, and enjoy.

If you have any more specific questions let me know and I'll try to help you.

Good luck!