Starting from scratch to plant new lawn. Zone 10a : 30 to 35 (F) Southern California

I've heard and read several different things about what to do, and some things seem contradictory. Wife and I want to get a new lawn planted this Fall (probably seed for cheaper $) for our kids to play on. The current lawn (or what is left of it) is bumpy with dips, and is mixed in with some weird bermuda or augustine. Do you think this job is DIYable for a total newb.. or are we gonna have to drop some $ on it? I've been reading a lot about DIYing it but there just seem to be too many different approaches that make this confusing. What precise steps should be taken?

EDIT: here is an image of the current state: https://ibb.co/kfznQQ