Setting up an online chat system

Hi,

I have been asked by my manager to look into the possiblily of setting
up an online chat system for our external website.

Basically, it will run on the website and its purpose will allow
members of the public to access the chat room and discuss current
topics with experts. Similar to a doctors interactive website where
patients can speak and get advice from their GP.

Anyway, Ive never set up anything like this before so dont really know
where to begin. The chat system may be something that we would need to
pay for but ideally it will have a professioanl appearance and be easy
to implement (please).

Any help would be much appreciated. Thanks

Burnsy