Timming Chain Noise-Nissan Altima-1995.

I own a nissan altima,1995 with 305,000 kms odometer readings.

Recently this car which otherwise was running fine, has started to give problems.Some of the problems are as follows:-

--after starting the engine,when its' in the rev--there would metallic noise coming from the engine compartment

--While backing and the steering turned fully towards right, there would be sharp metallic noise.

-If the engine is idled after the vehicle have run for a while there would be hesitation.

My mechanic told me the essential problem is due to timing chain, either the guide is loose or broken.

Any idea of fixing timing chain related problem,cost involved,or get to know if it the root cause of the problem.

Thanks.

P.Goswami.