he_ros_
The whole installation process of GrapheneOS is very very simple. Follow the Instructiuons and press a couple buttons and you are good to go.
Like mercury said, bricking a Pixel while trying to install GrapheneOS is extremely unlikely and not really a concern.
I flashed GrapheneOS on 3 Phones already. My Pixel 7, A Pixel 8 for an Acquaintance, and a couple days Ago a Pixel 9 again for me as upgrade to the P7.
Because I had two phone I switched all data over manually. All pictures I copied onto my PC. And didnt bother to copy them to the new phone.
For apps with important local data I used the Apps Export functions to export configurations and data and saved it to my PC manually.
On the new phone I installed my apps normally and when I had an App where I have backup files I copied the backup onto the phone and used the apps import function.
To get quickly get files from my PC to my phone and vice a versa I use LocalSend.
For the bulk picture copying I just hocked my phone to the PC and set the USB modus to storage mode and copied the image folders over to my PC. DCIM and Pictures are the two folders I copied.
It takes a couple hours to do the whole migration manually. having the old phone and the new at the same time makes some things easier, but if you diligently do all the manual backup you can do it with one phone.
I myself still use google services on my Phone. I use banking apps and the safest way to install them is with the PlayStore.
Using GrapheneOS even with play services is a huge improvement of Security and Privacy compared to Stock Android.
uff that text was longer than expected. I hope my rambling helps.