Xvid 640x480 how to?

I have clips recorded by samusung camera in 640x480, 30 fps and unfortunately coded by xvid.

I know that xvid is not supported by premiere pro cs4.

Please tell me what is the best format and preset (resolution, fps rate and pixel ratio) to encode it in adobe encoder to edit clips in native form in premiere. In my country we have PAL system. What would happen if I encode it to NTFC?

What is the best format and preset to export project wihout loosing quality and save good proportions? How to make widescreen of this project?

Please help me. I' ve tried to solve this problem by myself and now I am totally confused