Tweak and add functionality to existing WordPress site

Hi.

I have a WP internet site that I need to add functionality to.
I need a developer who knows WordPress and also PHP, MySQL, HTML and CSS.

I want to add certain things to my site which can be offered by existing plugins we can install, but there is a good chance we will need to tweak the plugins for my needs.

I need some good and reliable who can work quickly as this job is urgent.