You've received a few good answers. I have some non-biased information for you. ( Non-biased because I don't customarily work either in Tustin Ranch, or in Yorba Linda. Can I work in both of those areas? Of course - I'm licensed to sell properties anywhere in California. Frankly though, I try to stay in my neck of the woods, in South County.)
First piece of advice. Choose ONE Realtor, from either area, to serve all your needs. Most of us have our area of specialization, either attached to our name, or easily found within our profiles, which you can read by clicking on our name.
Of the agents who have responded to you - as I'm writing this - one has Yorba Linda attached to her name, and Cyndy SAYS that she has experience in both areas, AND asks you a very important question, regarding Proposition 60 which might apply to your situation, although I doubt it as you purchased your present property only 13 years ago.
Also, bear in mind that the agent you choose doesn't have to be a Trulia forum agent - this is just one of the ways to choose an agent to work with.
Another piece of advice, negotiate with the agent you choose - you SHOULD be able to negotiate some commission rebates or reductions, on BOTH transactions, if you end up selling one, and buying another.
Last piece of advice, if you can buy the new property without selling your present one, you can make your present house a rental, if you feel comfortable being a landlord. Most of us agents can handle ANY of these scenarios, and can advise you objectively, with YOUR best interests in mind.
Good luck in finding an excellent connection and getting some answers to your questions and options.