We've been to WDW many times, but we recently relocated and find ourselves 25 minutes from
Disneyland ! Our first visit is coming up this weekend, any advice on what we absolutely need to do, see, or eat
First off, welcome to SoCal!!

We just moved here from the S.F. area. I've been going to Disneyland all my life, and have been to WDW seven times. Before others chime in and direct you to other threads, I'll offer my personal thoughts based on more than 150 visits, including nearly 20 visits in the past three months.
Get an annual pass if you can. Disneyland is very expensive. Now that you live here, you can even take advantage of the payment plan. You have three annual pass options: SoCal Select, Deluxe and Premium. There's also the Premiere Passport, which includes WDW if you think you'll be going back there in the next year. I have the Premium AP, which includes parking and some good food and merchandise discounts. With the payment plan, it's honestly the best way to go.
Next, see the attractions that are not at WDW. Like Alice in Wonderland, Haunted Mansion Holiday and Indy at Disneyland. Of course you have to see Carsland and Radiator Springs Racers's at DCA. Then take your time. I think you will enjoy comparing the attractions that are found at both resorts. Don't be surprised to realize that many of these are quite a bit better in Anaheim. But WDW gets the edge on a couple of them.
If you find yourself feeling nostalgic for a little bit of WDW by nighttime, see Disneyland's fireworks show "Remember...Dreams Come True". It's actually a great introduction to our park, with the music from Wishes. I think it's one of the best Fireworks shows around.
Food wise, I recommend trying Café Orleans at Disneyland. Sit outside and take everything in. Blue Bayou is always going to be there. Save it for a special occasion...or not. We ate lunch at BB yesterday, and it was overwhelmingly OK. Over at DCA, Flo's V-8 Café is a nice counter service place in Carsland, where you can be immersed in the experience, and have an enjoyable meal. But Carthay Circle Restaurant is the best place to dine within either park. I'd absolutely recommend a meal there.
Don't get caught-up in the "we have to do everything" mentality. You live here now. Disneyland is always going to be there. And it's only 25 mins away. We live about the same distance from the park. Some evenings, we can actually hear the fireworks from home. Just a reminder that we live so close to the magic.
Again, welcome to SoCal. Enjoy your new home park.