i have a new timing chain and gears kicking around, was wondering when the service interval is or when its a good idea to change this component.
i have 110,000kms on the clock.

also was wondering how hard this would be

 

Unless you are doing a complete rebuild run the original chain until it drops. Not usually worth the hassle of ripping off all the front end accessories, the balancer and and dropping the the oil pan to get the timing cover off. I've run factory chains up past 250K miles. Outright failures are rare. Stretching the snout otta the factory chain is very common.

If you just gotta have peace of mind on this then, yes, 100K miles would be a good time to do this.

Word of caution- CHEAP parts store chains stretch like salt water taffy within a few hundred miles. If you're not paying around $50 for a chain, it's probably not very good. Before installing the new chain always soak it overnight in a pan full of oil. If you can throw some moly lube in there, so much the better. Don't put them on dry if you can avoid it. Giving the chain good lubrication in it's first couple of revolutions will go a long way to making it live a long and happy life.