The DMV hearing is administrative in nature. That is, no matter what happens at the hearing, it won't dismiss your case. That matter gets heard separately in criminal court. The DMV hearing on a DUI is strictly about whether or not your license will have to be suspended.
As part of this, you have a right to have the representation of a lawyer, and that's recommended, because what you say at the hearing could potentially be used against you in the criminal proceeding. But you would also have the right to challenge the evidence against you, cross examine the state's witnesses, to put on witnesses of your own if there are any and to testify yourself.
The standard is not proof beyond a reasonable doubt in an administrative proceeding. If the officer's testimony is even slightly more convincing than yours, he will prevail. The burden of proof in these hearings favor the state.
If you can convince the judge that there was no probable cause for the stop and the arrest, you have a chance of prevailing, however, since that, along with evidence that you'd been drinking drinking is what the magistrate will be looking for.