I am designing a logo for a friend. I have the font and colors done. All I need is an icon for it. I found a vector on shutterstock that would be perfect. I took the vector and used it as a base and re-designed it so it's completely different from the original. Should i be worried about copyright and licencing.
Yes. You should be worried about copyrights and licensing.
Royalty-free stock imagery is typically set to strictly forbid use in a logo. Shutterstock specifically states that logo usage is not permissible on their site - unless you purchase the rights to the image which can cost considerably more than typical royalty-free costs. You will find this rather common among stock image providers.
And be aware, there is no such thing as "edit the image by X amount and it's okay"