Sending device back to Microsoft through support, but need clarity on process

Hello, got a Microsoft Surface Laptop 7th Edition, and it has stopped working with a year, it is under warranty. The key issue is it will not turn on. The windows logo keeps flashing but it will not turn on. I have tried all trouble shooting from MS support forums and online communities. The last option is to send it back to Microsoft, I was about to arrange for the pick up, but I had a few questions

• Before the Microsoft folks start to replace parts or add something, and if that is not covered under warranty, how do they communicate with you?
• The final message on the service order page said, I would agree to any additional cost that may not be covered, but do I get to decide if I am okay with the extra cost, I am unable to contact Microsoft support to get these answers

thank you