One, is the oilpan bolt pattern on the Renesis the same as
the 13b?

No.  I think the front cover is all that's different though. 

Will the Conversion Concepts mount work for the Renesis without modification, and if not, what mods are necessary?

Best to talk to Fred about that.  I'm sure he's either got a new mount, or will have one soon that works for the Renesis. 

Two, (big newbie question here), where do you actually GET
a Renesis?  Is there a crate version available, and from
whom?  Latest price?

You can buy one direct from Mazda, but I'd recommend calling Bruce Turrentine instead.  Last I talked to him, he was selling the engines for $5700, which includes having him personally go through the engine.  If I were starting over, that's probably the way I'd go.  

(On this list and the Canard Aviation forum, it's been between $5700-$6200) Has the RX8 been out long enough to make it worthwhile sourcing one from auto wreckers, or are they being snapped up by speed shops and racers?

I've seen some used engines for sale, but they aren't necessarily a bargain.  Eventually, there will be more deals out there though.

Is the Renesis overkill?  Can i get 200hp out of a n/a
13b without a lot of exotic modification? (I've been
reading the posts on injectors, intake tuning,
turbocharging, etc).

Truth be told, I don't think the Renesis will really outrun the 13B in our rpm range.  I think Mazda just made a better intake, and turned up the rpms.  There are certainly some improvements in the Renesis, but it's not light years ahead in performance.   It's absolutely possible to get 200 HP from a 13B at less than 7500 rpm, with nothing more than a street port, and a decent intake and exhaust.   Tracy was doing it, and I expect to be as well.  All that being said, the Renesis is clearly the future of the rotary, and there's no downside with the exception of a bit higher price at the moment.  I think the Renesis is a slam-dunk choice for folks starting out now.