You can preview files if you have set a program to use for previews in preferences - directories and then right-click on a download and select preview.
About continuing downloads: amule is 100% compatible to emule in its files, so you can continue downloads started with emule (and any other client that is compatible with emule, I know there have been troubles regarding edonkey / overnet clients that brought along their own file standards...) and you can continue downloads started with amule under windows using emule etc. The only thing is that amule will complain about files being possibly corrupted and rehash all of them which takes some time...