A DUI is different from state to state, whereas different states have different laws and different towns in the same state even handle DUI's differently.
For the most part, if there was nobody hurt as the result of an accident and it was his first DUI, than they will likely want him to attend a traffic school type of course, they will also impose a small fine and likely he will have to go to court 2 or 3 times depending on how quickly he does all of the things that the judge asks for.
I've never had a DUI personally, but I had to help get a few people out of them. They had to attend 10 hours of drving school in a small group, then one large class and a small fine, about $200 or so.
If you get a lawyer, you will be out a good $2500.00 or so and he will likely just repeat whatever the judge says. Unless you get a very good lawyer, who is very experience in these matters.
He will certainly get bombarded with a ton of mail from lawyers, because they seem to get mailing lists of people who just got DUI's and send out mail solicitations, but have him call more then one, sometimes the first lawyer that you call isn't too great.
Just interview with a few, they will discuss the specifics of your case, what kind of evidence they have, how strong of a case the state has and tell you what your options are, use your gut instince about the lawyer.
Also make sure that he notes when his temporary license expires, they usually give him a paper when they take his license telling him that.
If he doesn't complete all of the requirements before the expiration, he can petition the court for an extension, that way he can keep driving.
And if the car was impounded, take it out immediately! They can charge up to $200/day! So that can add up.
Good luck