Preload Movie: The easiest way to do this is to have each swf have a blank first frame with a stop action. That way you can use load all of them in advance invisibly with load movie commands, and all you have to do when you're ready to use them is make sure you tell the clips to go to frame 2.
Gif Replacement: FLASH 5: "File" - "Publish Settings" - and in the "FORMATS" tag, select "FLASH" "HTML" and "GIF" then under the "HTML" tag select "Ad 3 Banner" (or "Ad 4 Banner") and then under the "GIF" tag select "animated" (if you wish). The code that this publishes seems to work in IE5 and in Netscape.
Put DHTML Over The Top of Flash by putting the following line in the flash object section:
<param name="WMode" value="Transparent">
This line makes it possible in IE, however, there is apparently no way to do it in Netscape 4.x. The only (not so good) way to do it, is to put the flash in a layer, and HIDE the layer (visibility:hidden) when the DHTML layer goes over the top of it.