if you want a frame accurate cheap solution get virtualdubmod from here http://virtualdubmod.sourceforge.net/
you can do all the color correction you want with filters and it's especially useful when assembling shots in a sequence, you can't edit like you can in premier, but it allows you to make precise cuts from footage, and output certain selection as a file which you could then reassemble back in premier.
regarding combining pal and bntsc footage, the aspect will be different,
widescreen non anamorphic NTSC is 720 x 272ish, pal is 720 x 325ish
now as the width is the same, it makes it hard to just vertically squash the footage down because it's just that, squashed.
I don't know of a way to convert a widescreen item from PAL to NTSC 'and' keep the correct aspect ratio. normally when I do something quick and dirty for work, I just crop some of the black bars off top and bottom to change 576 to 480 without losing any of the image.