Is there a sure-fire way to determine if an MCU is fried?
You could try wiring up the bare minimum you need - supply and ground pins (decoupled), MCLR, PGC  and PGD - and seeing if you can program it. If that doesn't work the only sure way to find out if the chip is functional is to get another one. If that works, the first chip is faulty.

I always buy at least two of any MCU.