2000 S430 Died
 

Car just died in the school parking lot, when the key is turned it 'clicks' which leads me to believe it is a battery but I am diagnosing with my wife in the car which can be challenging. She also says that next to the time/temp display on the dash is shows "PW". Any ideas ... is the battery the problem?

could also be a starter but check batt first.you say car just died which means batt could be flat because alternator died.

If its the original battery, I'd put my money on that first. Start with the cheap odvious stuff, like a 7 year old battery.

Yank it and bring it to an Autozone they will load test it. Or you can call MB roadside and they will replace it, usualy for only the cost of the battery plus tip, so not a bad deal.