Since both parties are in agreement, and there’s no children or property involved, it should just be a matter of going to (or calling) the courthouse (try marriage license department) and asking where to obtain “no fault” divorce forms. You should be able to get one at or near the courthouse. You don’t need lawyers and it shouldn’t cost more than a couple hundred dollars for forms and fees. Buy the form (make sure you get the right one), fill it out and mail it to her for a signature, have her mail it back to you, and file. You’ll be divorced in short time.
Getting lawyers involved will send your expenses through the roof, even if the case doesn’t go to court, so avoid this if at all possible. If you do need legal help and don’t have a high income, you might be able to ask for reduced fee legal assistance - ask at the courthouse or the place you get legal forms from. It will still run you at least $5-600 though.
Caveat: I am not a lawyer, and I don’t know if the location you got married or the fact that she resides out of state makes any difference. But the fact that you’re both amicable is the key to a cheap and hassle free divorce.