Wairau,
You might want to look at the book "Engineering Documentation Control Handbook, Configuration Management in Industry" by Frank B. Watts.
This book is more on the practical side than most others and has an extensive discussion on interchangability of parts which controls when a part gets a new number or is just a rev.
In your case the PCB would get a part number and probably would have a bill of materials associated with it. If the PCB is changed and is still interchangable it will keep its current number but with the next rev number. Part numbers should not contain the rev because the part should be interchangable. Dash numbers are sometimes used for various reasons but should not be a way of controlling revs. Generally what I've seen is that dash numbers are used to group together some parts that are very similar.
There have been several discussions in this forum similar to your question so it might be informative to do a few searches to see what you can find.
-Mike