arkdestro on "someone hacked and changed my admin details"

hello admins i am having a big issue, i run a development company.
one of my worker used to work in a website named vineyardindia.org
he left the company and changed the admin email and the password
i have the old ones but doesn't know how to use them to login to my WordPress admin area, is it possible if i provide the old details and credentials i can recover my admin.
since its a clients work,, asking him for the cpanel details and getting into the database is out of the question.