MacBook repair outside warranty?

Do not even attempt to touch the SSD chips on the Logic Board. The data on the SSD chips is hardware encrypted on the 2018+ Macs and requires the security enclave chip to be able to unlock the data on the SSD since the security enclave holds the encryption keys used to unlock the SSD & decrypt the data.

As @Mac Jim ID mentions, you will need to contact a professional data recovery service to see if they can retrieve your data. If the data is that important to you, then you will not want to mess with the Logic Board yourself as you will most likely destroy the data. You will likely only have one chance at recovering the data, so choose wisely.

Unfortunately I recently saw a video from a respected repair tech who performs Apple Logic Board repairs who mentioned that in the majority of cases the failure of these boards is due to a critical component on the Logic Board related to the SSD which destroys the SSD. Just hope your Logic Board failure is something other than a burned out SSD chip.

People should always have frequent and regular backups of their computer and all external media (including the cloud) which contains important & unique data. The more important the data, the more backup copies a person should have. As you are finding out the hard way, there are a lot of new ways to permanently lose access to your data with these newer Macs due to all the hardware, software, and security changes. Apple includes the Time Machine backup software with every copy of macOS in order to make it easy for people to backup their Mac and external drives.

I wish you luck in recovering your data, but you should be prepared for the worst here since it is difficult to impossible to recover data from SSDs especially when the data is hardware encrypted.

As with any warranty, the expiration dates are hard dates without exception. I have not heard of Apple doing any out of warranty repair unless it was for a recall.

As for recovering your data. There are data recovery companies that may be able to help, but unfortunately I am not able to recommend any. Finding a legitimate company may be difficult and will require a great amount of research as there are also many shady companies that will take your money without providing you the data you need. You may want to compare the cost of that service to the repair cost.

Doing it yourself may be possible, but I would not recommend that approach for data that you deem to be priceless. Others may be able to offer the steps needed to do this with a higher degree of certainty that I would not be able to provide.