BMW 740 Timing Chain Replace/Remove

Hi Wanted To Know When I Should Get Maintenance Work On The Timing Chain. At What Miles Should It Be Change?

I Have A Loud Taping Noise Coming From The Lower Part Of The Engine. My Local Mechanic Says It's The Glide For The Timing Chain. How Hard...

I Was Told That My Timing Chain Is Going Out Or The Timing Belt Im Not Sure If Its A Chain Or Timing Belt Or If There Is 2 Seperate Timing...