Hi, I am probably the only person applying that has actually passed the freelancer security exam. I also hold a CompTia Security+ certificate and qualified and Linux and server hardening.
What I can do for you is, to check you site for vulnerabilities, identify any files altered, fix issues, remove your mailer program, and install a security plugin for the site to prevent further attacks.
Once my work is complete I will have to get you to also change all user passwords as the attacker may have downloaded your DB and have direct access to your site now.
Please note that this is a very time consuming process and my bid is for my work and time.
Lets discuss.