Just to get your knowledge base up you can do two basic things,,first,,watch for a big rv show in your geographical area,,and then just go and look at different models and floor plans just to visibly see what's available.
For more "operating" info,,there are about 3-4 good rv forums that have category threads pertaining to 5th wheels and rving in general. Nearly all of your questions will have already be posed by ones before you, so just get into the 5th wheel category and read all the old threads on topics you want to educate yourself about. It wont be too long before you will have a good knowledge base.
Once you start paring down your list of options for 5th wheels, you can usually find an owner's forum that again will be a wealth of information that pertains to that manufacturer and perhaps even the model that you are interested in.
Expect to be a bit confused by all the terms, model numbers and etc,,but over time, things will begin to become clear.