Hey Steve,
This is the industry i work in. Online Marketing - SEO/SEM Advertising.
Have you checked out the Google AdWords section already?
http://adwords.google.com.au/ That would be something to get you started on.
There are no simple sites to turn to for people wanting to learn about this sorta stuff. Well.. none that i've come across anyways. There are forums but they are more focused on industry specialists (nerd talk)..
I can definitely point you in the right direction for assistance though. I've worked with some smaller companys that focus purely on assisting small business owners with their online advertising. Like a one stop shop.
http://www.reachlocal.com.au/http://www.yodel.com.auBoth are companies that operate in Sydney.
Reach local have a great proposition. A lot of their reporting is fantastic and accounts are taken care of.
I used to work for yodel and assisted in them becoming the first reseller of Google Adwords in Australia.
Compare prices and see what would fit best for you. Oh and speak to a consultant. They'll all be very young no doubt and having worked in Operations part of business I disliked most Sales reps but there are a few decent ones around i guess
Cheers,
Kevin