Check out the following sites, and then consult directly with an experienced TX defense lawyer with any specific questions. Good luck.
DISCLAIMER: I do not practice law in your State. This answer is provided for informational purposes only. This answer does not constitute legal advice, create an attorney-client relationship, or constitute attorney advertising.
You may be entitled to get this case expunged under Texas law, so long as you have successfully completed all of the conditions of the deferred disposition. If you take no action, your arrest record will always reflect that you were arrested for this offense but that the case was dismissed. This is not a conviction and you are entitled to say that you have no convictions. If you do not expunge this case, you would still have to acknowledge that you were arrested for this matter. I always recommend (and I think most conscientious defense attorneys would recommend) that my clients who are entitled to an expunction should petition the court to erase their records. It saves you from the situation where you deny a conviction but the employer sees the arrest and believes you to be deceitful.
You would have to speak to some Austin criminal defense attorneys to get an idea of how much people charge, but in my experience, attorney's fees for this kind of petition fall between $500 and $2,000, plus about $400-500 in filing fees. Give a call to some local criminal defense attorneys to see if you qualify and what they might charge for this case.
Disclaimer: This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.