Can I represent myself? What can a lawyer do for me?
You have a Constitutional right to represent yourself although it is strongly not recommended. Drunk driving is a very complex area of law with increasingly harsh penalties. There is a vast amount of procedural, evidentiary, constitutional, sentencing and administrative license issues which are unique to DUI law and can take an experienced attorney years to become proficient in.
What can a lawyer do? A qualified DUI attorney can review the case for defects, suppress evidence, compel discovery of such things as calibration and maintenance records for the breath machine, have blood samples independently analyzed, negotiate for a lesser charge or reduced sentence, obtain expert witnesses for trial, contest the administrative license suspension, and successfully defend you at trial.