What if you are arrested but not charged?

Although I do not practice law in the State of New Mexico, here are my initial impressions.  While being a first offense will be taken into account by the prosecutor and the judge, it is hardly the determinative factor.  Anything can theoretically be dropped from a felony to a misdemeanor for the purposes of a plea  -- it just depends on several factors, including but not limited to the strength of the state's evidence and the ability of your attorney to negotiate a plea.  That being said, in response to your question, it is clear that what you can do is hire a criminal defense attorney as soon as possible.