2001 Leganza bought in 10-2007

2001 Leganza bought in 10-2007 with 122K miles. 2.2liter DOHC engine with 5speed. Sweet car, but always felt the valve noise was a little clanky and noisy for a small 4 cyl engine. Last Saturday with 126K miles the timing belt failed. Daughter admitted that the oil pressure light was on for the day just prior to the event and that morning. How fatal is this event to the valves in the head? Could the oil pump have brought this on with cam shaft seizure? Should I replace the oil pump anyway to be safe? Havent't goten off the time belt covers or under the valve covers to spin the two cam shafts to see if seized or free spinning (cam lobes against the valve springs. Is it likely that there is no valve damage? I need to examine the belt to see what kind of failure is suggested. I suspect it may have been stretched and too loose, hence the noise/whin. On this car the first replacement belt was at 30K by a dealer. Should I take this as an opportunity to redo the head which has 16 valves? Or, Should I get a used motor with 50K miles instead?