flash actionscript: How can I load in one movieclip, have it play, then load in another movie clip and have it play, then have the whole thing loop?

There are many ways. the easiest is to place a line of coed in the last frame
on them movie and have in load the next movie.
Example loading both movies into a Base level movie (Index level and loading
the loos into movie clips)
createEmptyMovieClip("loop_mc", 20);
loop_mc.loadMovie("FirstMovie.swf");

In the last frame of the FirstMovie swf have this line
_parent.loop_mc.loadMovie("SecondMovie.swf");

In the last frame of the SecondMovie swf have this line
_parent.loop_mc.loadMovie("FirstMovie.swf");

This thing will loop forever!
You will need to break this someplace using
loop_mc.unloadMovie