How long do integrations take?

Our group are looking at outsourcing WMS to another provider, meaning I guess it will largely be up to me to manage the integration of this WMS system to NetSuite.

Is integration complicated to learn? How long would you estimate a single person would be working on setting this up? Do you quite often have to continue working on integrations afterwards?

I'm thinking about how all our bins, items, orders and more are all going to need linking, is that every field needs a mapping? Including mapping processes like creating new bins and locations so I'm not having to create both on each platform but just creating it in one and the integration doing the same on the other end? And making sure that Work Orders that are carried out in the warehouse on the WMS are also replicated in NetSuite?