WD6 / 7

Hi I've got a number of questions please. Firstly, if I upgrade from WD6 to 7, will I still be able to open all the files I've already made in 6. Secondly, I am producing a map of a town and want all the shops, banks etc to open as pop ups, Is there a recomended limit to the number of layers I can use on one page. Also at the moment when the page opens you can see different layers opening before the page is fully loaded. Is there any way of stopping this.
Thanks
Robin

In brief, yes, all sites created in WD6 will open fine in WD7.

I have not heard of any limit to the number of layers you can use.