The further you stay (hotel) away from the Expo location (Anaheim convention center), the cheaper it is. You can get ART tickets (bus) to take you to the location. I would stay on a hotel on Harbor, Katella, or Ball (convention center is at Katella & Harbor).
You should be able to get discount
Disneyland tickets through the
D23 expo website (there's a special link). If you are a D23 member, you should get the tickets earlier rather than later (the closer to the expo you purchase the tickets, the less of a discount you get.) I'm not sure if you can get discount tickets if you are a free D23 member or if you have to be a gold D23 member. If you have to be gold, you should also be able to purchase discounted tickets for your guest.
D23 members can get into the expo an hour earlier than general admission.
Places to eat: one of the hotels next to the convention center has a food court. There may also be food trucks, otherwise plan on eating inside the convention center (they have food places set up inside).
Crowds are high, plus the Expo will happen in mid July (during Disneyland's 62nd birthday) instead of the typical August.