Finally ready to move on from our f’n lawn. Now, where do I start?
Located in zone 10a, Silicon Valley. Our entire front yard is currently Crabgrass. To give the new plants a chance, do I need to remove the top layer of soil, with the Crabgrass? Then lay down fabric and mulch?
Any advice is appreciated.

Cover your entire yard in cardboard box remnants, make sure there's no tape or other material left over when placing the cardboard and cover all areas you want crabgrass removed. Then hose it all down to really help it along and to keep it from blowing away. Soon the crabgrass will be dead and you'll have a clean canvas of soil to work from that has nutrients from the dead crabgrass as opposed to removing all that.
You forgot the important part where you cover the cardboard with woodchips or topsoil. One or the other, or both, depending on what you're going to do with the space.
Roughly, how long will it take for the crabgrass to die off?
Earliest is probably 6-8 weeks to play it safe, but here's some other redditors experience with it: https://www.reddit.com/r/NoLawns/s/7CRqT4Xt8p
And some other online resources: https://backyardhabitats.org/wp-content/uploads/2017/07/SheetMulchingEMSWCD.pdf Cardboard mulch after 1 year (composting forum at permies) https://share.google/sl5qVaB5pq5Oc3V9o
Awesome, thanks for the links.