1994 Nissan 300ZX broken timing belt

Driving at 30 mph, I heard a slapping engine noise, the engine stopped running and I pulled over. The timing belt broke! I am in the middle of putting a new one on. After draining the engine oil I looked for metal flakes ( I was told that this may be an indication that engine damage occurred) It was clear of foreign bodies so I have continued replacement procedure. I have been told the engine is shot by some and others say it is ok. My question is two fold; 1) Who should I believe and 2) how can I test valve pressure prior to starting so that I don't bend valves worse. Thanks