Good evening halicon! To answer your questions:
I run an RMR and my buddy runs a Kern. Ripboard also makes great boards.
You will need knee/shin guards and a cup. Be prepared to put your body through all kinds of abuse.
Riverboarding is like running wind-sprints while holding your breath. It is very demanding. You are not just floating down the river, hanging on to the board. I cannot emphasize this enough.
Ripboard offers demos. I would take one down to the play-park and see if this is the sport for you.
TEAM FLI :: Face Level sports - Forward motion, headfirst & horizontal to gravity!
is a great resource for riverboarding.
If you have any other questions don't hesitate to ask.