I am of the understanding that the hard/grass debate is pretty much a no-brainer: I.e. hard every time, largely because you can slide on it. I'd also throw in the consideration that every grass strip i've landed on has been somewhat bumpy, and that the grass around the runway probably isn't maintained as a strip.
WRT sparking, most of a PA28 is aluminium. That doesn't spark when you put a grinder to it, so I can't see why it would spark on a runway. Granted there are some components that might.
Altitude wise, yes(ish!) Only time I chose to fly on a 40deg day in that part of the world it was +20 at 9500, and turbulent through 8000.
Silence - you could always turn the radio (and the rest of the avionics) off, justified on the grounds of reducing the fire risk
I've already given my prescription, but basically I reckon keep everything as 'normal' as possible about the arrival - less chance of messing it up, who cares about the damage-on the ground stuff like stopping the prop. If you normally fly a flapped, powered approach, doing a flapless glide is likely to result in a worse arrival. Overall I think a little too much is made of it - so long as it gets flown on in reasonable shape, under control, and doesn't have anything to hit, it should only be scary for the insurance company, rather than a 'thank god everyone survived'.. but maybe I'm wrong - they did see fit to stick up a restricted area, fly around for 4hrs, etc.