Every state has a pool of private attorneys that they will tap when there is a conflict of interest on a case with an indigent defendant. It happens all the time. For example, if two of you were arrested together and neither of you had enough money for a lawyer, only one of you would get the public defender, and the other would get a private lawyer who does pro bono work for the state.
So you will have a lawyer and the fact that it comes from a different law firm than the one you have now is not anything that will get your case dismissed.
As for the informant, if your case goes to trial
, your lawyer would get the right to cross examine him and let the jury see that he came forward with information just to save his own skin. The jury would factor that into whether his testmony is credible or he's a liar.
If you didn't want to try this case and you have no criminal record
you could possibly get a special program -- drug court
is one -- that would allow you to get these charges dismissed after the completion of your supervision. Don't deal with the prosecutor yourself. You'll have a new lawyer and anything you say to the prosecutor cn be used against you. Let him negotiate something that will hurt your record as litle as possible.