I can't help on the first question, but someone will be along soon that can help. I change my belt about once every 2 years. Some do it every year. If it has been a long time I would change the belt tensioner and idler pulley at the same time. Also check your crank pulley, if the rubber is cracked I would change it also. You don't want it to fail. I have never done my timing change on my 02 R53, it has 139,000 on it.
Under normal use the timing chain itself shouldn't need replacement, however the hydraulic chain tensioner can fail and the nylon on the chain guides can become brittle and pieces break off. Keep an ear open for a strange rattling/chain noise from that part of the motor. Replace the tensioner when this occurs and if the noise comes back the guides might be bad.
