No one here can tell you what will happen at trial. Even your own lawyer who is familiar with all of the facts and circumstances couldn’t guarantee what the outcome of the trial would be. You should talk to your attorney. If s/he seems confident there is probably a good reason. As far as work not being done and the case being continued several times, all I can say is that the wheels of justice turn very slowly.
Where I practice in Wake County about 77% of DWI cases result in a conviction. I'd imagine it's about the same in Mecklenburg County. That's a pretty general statement - the facts of your case will dictate whether you're more likely to be on the good side of that %.
This is a conversation that you need to have with your attorney. No-one on this board can competently answer this question without reading the police report and reviewing the evidence. As far as what should you expect-this is another question you need to discuss with your attorney. A recent Supreme Court decision Lafler v. Cooper requires that an attorney discuss all pre-trial offers to the client. You want to know what the offer is currently and what the maximum sentence would be should you not prevail at trial. What does your attorney view the strengths and weaknesses of the case to be. An attorney can only advise you of the above criteria-no attorney can predict what a jury will do.