Key times for the probe tonight:
11:18 PM (eastern daylight time): deceleration engines start
11:53 PM: deceleration engines stop
12:07 AM: spacecraft orients solar panels towards sun
The NASA TV channel is probably going to be the best source of timely information. An online source likely have timely updates is this Twitter feed:
http://twitter.com/NASAJuno/with_replies
If the probe is destroyed or heavily damaged, one likely indicator will be the dishes aimed at the probe no longer receiving any downlink signal, which would be indicated on this page:
http://eyes.nasa.gov/dsn/dsn.html