In my experience, the answer to #1 depends on what types of file links you are using. Direct cell-to-cell references are easy: use Data Edit Links and then hit Update Values for any files linked in this manner. Other types of links, such as SUMIFs, don't work that way and give you #VALUE messages. My work-around there is to have an autorun macro that opens each file and then closes it (you don't have to have ALL of these files open simultaneously). That way, it's automatic when I open the destination file.
I believe the answer to #2 is No, the destination file has to be open.