I have 151,000 miles on my 2002 4cyl Camry and have not changed the timeing or the sepeitine belt: Is it time to have it done?

Depends on what you have done so far.
The transmission fluid should have been replaced, the timing belt and water pump, spark plugs, serpentine belt, radiator hoses, and fuel filter should have been replaced at 75,000 miles or before.
There should be a maintenance schedule in the back of your owners manual with some guides.

on the 98 toyota camry check that the gas cap is on tight or look at my fix on the toyota sienna that could be it or a vacumm hose could be split or leaking i would have these checked before you get into very expensive repairs look for the obvious first

No way. They usually don't wear until 100,000 miles. Some last for the life of the vehicle. I would change around this time. You should be good my friend.

1994 2.2 liter 4 cylinder is a timing belt, it should be changed every 90,000 miles under moderate driving conditions, under severe driving conditions (stop and go traffic, etc.) it should be changed every 60,000 miles

its timing belt. This car requires the timing belt to be serviced at every 60k miles. This engine is a non-interference motor, so the engine will not get damaged internally if belt breaks. But other parts externally can become damaged. Also at the same time the timing belt is changed, replace the water pump, idler and tensioner pulleys.

Timing belt change interval is 75,000 miles.

It's time to change the T-Belt and water pump now.

Water pump is directly behind the timing belt cover.

It's best to get the water pump done at the same time.

my automatic transmission light doesn't turn on when you turn the headlights on. Can't see what gear its in at night.

Yes those vehicles have timing belts instead of chains. I have yet to see a timing belt that doesnt need to be changed at some point. Maybe the tech meant you didnt need to change them now. Each manufacturer has their own mileage interval, but generally speaking, anywhere between 60,000 and 90,000 miles they are due to be replaced.

a timing belt is normally suggested to be done at 100,000km you can go longer but anything can happenafter .pierre

Replace the timing belt at 90,000 miles.

It will not damage the motor (bend the valves) if it breaks or jumps time

Finally, if you do change the belt, make sure that the water pump is inspected very close for any evidence of coolant seepage at the impeller shaft weep hole. If there is ANY evidence of wetness or leakage, replace the pump then. Easier to change the pump when the belt is off, than to have to do the whole job if the leak gets worse, and, if it leaks down the road, coolant on the timing belt will damage the belt, and you will have to buy a new belt, too. Change the plugs at 90 K miles, too.