ugent need seo expert help

[devat]

hello all

my url is : www.directconnectweb.com

in case my sites PR - 4 and most of k/w based good result got in search engine's top pages

but i have to need the help for :

link: www.directconnectweb.com/Directory/Web_Design.aspx

now i want to change the -

www.directconnectweb.com/directory/web-design.aspx

and most of pages for home page and inner pages

so how can it possible and keep the constant result in search engine as well as PR

so p'se urgent reply ASAP

Thanks