I would recommend simply downloading and trying the demo
In the demo, under the 'Help' menu, there are options for 'Help Contents', 'Quickstart', and 'Support'.
The Quickstart Guide sounds about right for what you want. It is a dead-simple guide to doing your first composite with simple instructions and screenshots along the way.
The 'Help Contents' link gives you even more options by including guides on more advanced features of the program, such as batch processing and hot folders.
Prior to getting PhotoKey 3, I never had any experience with the PhotoKey line of products. However, when I first opened it up, I was able to use it fully with almost no learning curve. Since you have previous PhotoKey experience, you should have an even quicker time getting used to it than I did!
Last edited Tue, 19th Jan 2010, 8:36pm; edited 1 times in total.