i have changed some of the pages, and would like the security of
having the old pages, which were high in the serps, to remain indexed,
at least until the new pages reach the top 3. they would redirect to
new pages.
there are difficulties if i have different filenames for the new
pages, is there a way to keep the filename of the new page, the same
as the old.
i would like avoid using a new file name and a 301 redirect from the old page

If I am understanding what you want to do, then this should work. If
not want you are looking for you may hit me with a paper towel.

Create a folder, name it something for demo purposes I am calling it
"newpages", add all of your new files into the folder. then your
redirect string would look like this
"http://www.yoursite.com/newpages/file.html" this will allow you to
use these pages and still keep the old ones active while the names can
remain the same.

Hope that is helpful.
lru