Andrew Kramer made a preset and tutorial that might be helpful.
Johnny Cuevas, Editor
"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.
To resize the comp(s) you can use the "scale composition" script that comes with AE to resize everything. The script scales all of the layers down for you and keeps everything including all of the animation intact. Go to File>Scripts>Scale Composition and enter a new Height value of 576 and hit the Scale button. Then go into the composition settings and choose one of the PAL DV presets, either standard or widescreen, to set the correct width and pixel aspect ratio. Since your original comp is widescreen the sides will be cut off if you go with the standard setting. If you use the widescreen option, you will end up with gaps on the sides, which can be fixed by adding a new null, parenting everything to it (except cameras and lights or layers that are already parented to something). Unlink the scale width/height parameters and set the width so your layers fill the frame correctly. Also turn on the "toggle pixel aspect ration correction" button at the bottom of the comp window to view in widescreen.