If you drove 25 miles with no oil pressure, you have likely messed up the engine. However, that may not have occurred. I just wanted to make sure you (and other readers) understood the difference between oil level on the dipstick and oil pressure in the engine and their relationship to each other.
Your oil sending unit may have become disconnected or something to cause the zero reading. So don't panic yet. As for the smoke from behind the timing belt cover, that doesn't sound too good. Just get it checked out by a reliable mechanic and report their findings here. You'll get good advice on how to proceed.
