Hi, 
I was tasked with the decommissioning of few objects and their metadata, not anymore essential for business. 

based on one of the document by the developer whom i have replaced,  
there are around of 8 objects:
obj1.obj2,......obj8. with around 70 fields each.
51 apex classes and test classes.
triggers,
lightning components,
vf pages,
static resource,
custom label,
custom metadata, 
email alerts, 
email templates, 
named credentials, 
remote sites
quick action, 
workflow rules, 
process builders, 
community, 
sites, 
profile, 
validation rules, 
sharing rules, 
custom settings.

i just have to build a step-by-step process of how to break the links these objects have with the rest ongoing ones and delete these.
like, i cannot delete a field if it is used in a class. 

where should i start , if i should not mess up any ongoing process tied to these.
for what questions i need to have answers.
what all things i need to look into before starting. 

the person who previously worked on this left, so i do not have any one to suggest me. 

please advice me with your approach.

Thanks!!!!!