You were right about the man pages. Sed is one of the most useful tools that you have at your disposal, it would really benefit you to learn as much as you can about it. But I too want a quick answer every now and then so here it is:
sed 's/\\/\//g' <INPUT FILE>
Replaces the slashes. Note that you need to use escape characters in front of those slashed to keep from getting sed confused. The g at the end tells it to replace all instances instead of just the first one it finds.
sed 's/;/:/g' <INPUT FILE>
Ditto, but for the semicolon.
Hope this helps,