Timing chain replacement questions -> trying to find the best fix for "marble noise"

[SlideWise]

Ive got a few questions as to how reliable the ka24de's (91 s13) timing system is.
Do the chains and gears wear out easily(say after 200+k miles) or can you just replace the guides and tensioners leaving the original chains and gears? Is it the upper timing chain that is most prone to failure leading to damage or catastrophic failure or is the lower chain just as likely? Also how much play in each chain is acceptable and when should i start to be concerned?

Im trying to figure out how far into the timing system i should go and how much i should spend since i have the "marble in the valve cover" noise coming from my ka's timing system. Some people also say to just pull the upper chain guides as nissan rendered them useless but i dont know if i would consider that to be a proper fix or not...?

Any knowledgeable input is greatly appreciated!