In need of a company that provides Professional IOR Services

Hello folks,
I’m pretty new to this forum. Glad to meet you all. I think this is a place where I can clear all my concerns regarding importer of records. I am in need of a company that provides professional IOR services online ( https://tecex.com/importer-of-record ). But, before approaching such a company, I want to clear some doubts. What are all the documents to be produced before them for a service? How much would this kind of companies charge for their service? What are the factors to be noted while signing an agreement with an importer? Will the importers be responsible for the goods? Are there any rules for customs valuation worldwide? I know, it’s not much easy to give an answer to all my queries. So, please provide me the details if you are familiar with any of my concerns. Thanks in advance!