transfer from subdirectory to root

[Barbie]

Could someone help me... I set up my oscommerce store in a subdirectory "mydomaine/web/oscommerce/ " while my old site was turning and now do not know how to slip it to replace the old site. My web hoster said I'll probably "break" the new store if I do. However if I don't the spiders don't find it (set up Google siteplan) so I need to take the plunge. Help! :