Planning a disneyland trip in Anaheim, CA.

I am not great at planning trips/vacations because i tend to get too sunk into it. and overthink. but also get overwhelmed.

i am planning on going to disneyland sometime in mid march with a friend. neither of us has ever been. never been to cali as well.

with disneyland, do you need separate tickets as well? or is it just walk in?

also, how is the weather in mid march?

what are some things to know to plan a disneyland trip?