You cannot "expunge" anything in California. We don't have a true "expungement" law. What you're probably talking about is a dismissal under Penal Code 1203.4. Everybody calls that an expungement, but it doesn't take it off your record.
First - you may not be able to get the dismissal yet. You have to be off probation and have no charges pending. If you were placed on 3 years of probation, you have to get an early termination of probation before you can request the dismissal. If it was 2 years probation, great - you can try for the dismissal now.
Can you get it reduced to a misdemeanor? Not every felony can be reduced. If it is a "wobbler" (meaning it can be charged as either a felony or a misdemeanor), then you can seek to have it reduced, then dismissed.
Can you do this yourself? Yes, but unless you know what you're doing, you stand a good chance your request to do anything will be denied.
Is the price fair? It's in the ball park. Shop around and see what others are quoting you.
Despite the name of the website, answers given are for information only and do NOT constitute legal advice. Every situation is unique and the complete case (all the facts and information) must be discussed in detail before an opinion can be given. Do not rely on any answers given on this site without consulting face to face with an attorney licensed to practice in the jurisdiction where your case is. Any answer given does NOT form an attorney-client relationship.