No problem but you need to do it in 2 steps or two insallations.
Steps=====
*)-first backup your entire site from your site control panel cpanel/plesk etc.
*)-install the new version under a folder call it "app" from your root
*)-do the upgrade as stated in the upgrade topic.
*)-now after you confirm you have the new installation under "app" folder is working
and you have moved all your work etc. delete or move all old installation files and folders
to a new folder called it "backup", so now you will have only 2 root folders, "app" and "backup".
*)-it is easy now to move all "app" files and folders to the root folder.
Of course we can do this for you as a 2 hours custom work $100 if you want.
Thanks
Mewsoft Support www.mewsoft.com