The back of the third row seats folds to the level of your wood panel. That styrofoam piece under the wood panel is where the folded seats lie. I just pulled the seats out of my 13 and I'd be completely surprised if the holes aren't there on the 5 seater. It wouldn't make any sense to not drill them as it's going down the line. I did not remove the seatbelts as I didn't want to mess with all the D pillar panel (I break clips a lot). And I didn't even think of the airbags -
The other things you'd have to worry about is the latches that hold the seat backs down when you fold them forward. Which means you'd either have to buy new side floor panels (where the tie down hooks are) or cut that up yourself. and there's a plastic panel that the 6 central bolts bolt through on the floor - although I'm not sure what it does, might just be a trim piece. About the only way I'd tackle that project is if I found one at a junkyard and got to disassemble it myself to see that I got everything.
Interestingly, the dealerships near me said that there was no way I could buy the parts to make it into a 5 seater - a couple pieces of wood, styrofoam, and a bracket...Sounded a little implausible, but whatever, I'm just hacking up some wood until I get something that works for me.