I did the switch to graphene on my pixel 9 pro recently and have 0 regrets. it's just a better OS than the google infected android. Here's what I did:

* Follow instructions to install graphene on their website: https://grapheneos.org/install/

* Set up a private space which will be used for google play services required apps (bank stuff, etc). Install google play and google play services in the private space. Do not install google play services on your main profile. Set the private space to lock after 5 mins of inactivity. Set up google play on a brand new google account. You'll need to provide a phone number during setup. I used my normal phone number, others who are more concerned about deanonymization could use rental phone numbers or other things. Install any apps into the private space.

* Try to install apps on your main profile, ideally open source, privacy respecting stuff. Some recent apps I've found that work great and replace google infested stuff - AntennaPod for podcasts, OrganicMaps for OSM maps, Obsidian for notetaking (google keep), KOReader for ebooks, Molly/Signal for messaging. Vanadium as the default browser works well, except it doesn't have adblock plus for youtube (it does some other ad blocking though and works fine).

Things I still don't have a great solution for:

* Android auto - I don't think it works from a private space due to auto locking. Still figuring this out

* Spotify - since it also needs to run in the background and I haven't found a better music replacement.

Overall graphene has been a far better experience and I like it much more, and feel more in control of my hardware.

You should be able to install Android Auto, Google Maps, etc. in a separate user profile with Google Play on and no autolock.