Is it possible to put some transition effects (fade in and fade out) using quicktime pro before and in between clips?

And how do i export the movie without losing any quality? i tried exporting to avi with the highest settings but there was a noticable loss in quality.

you can't add transition effects using pro though... beside exporting will always have a quality loss if you prefer minimal quality loss you can try exporting to quicktime to quicktime movie -> TGA, Animation, Blackmagic Setting but those are extremely big file size, for smaller size go for sorenson video 3 compression.