Your last question is the easiest to answer. The office of the public defender are the pro bono lawyers for criminal matters. The staff at the courthouse can give you an application to their office. I would suggest calling a couple of defense lawyers in your area as well. You don't know what you can afford until you ask. It's standard practice for us defense lawyers to give people a free phone call (and usually a free in-person meeting) to discuss the case up front.
Regarding payment plans, we can't do pay-if-you-win because the judicial rules prohibit it. But we can do payment plans. Many attorneys do not do payment plans because it is a big business risk. But some do. I suggest you compare a few lawyers to see who makes you the most comfortable.
Regarding what you should expect in court, that really varies on the facts of each case. There are multiple levels of obstructing legal process. I suspect you are charged with the gross-misdemeanor level, but I can't be sure. You should speak privately with a lawyer or two to get a better idea of what you are facing.
Finally, I advise you don't put the details of your arrest online, since anything you say can be used against you in court.
Best of luck to you.
Obstruction of legal process and disorderly conduct on the police is often code for "you annoyed the police, so we charged you with a crime." Fortunately, this is often not successful for the state. The state has a high burden in the face of your first amendment rights and right to physically occupy a public space. The state has to prove you physically obstructed the officer from engaging in his lawful duties, and for disorderly, they have to demonstrate fighting words, threats, or some combination of words and actions that would tend to breach the peace and be a call to violence. Stop talking about jail and fines. You need a lawyer. If you can't afford one, you should apply for the public defender. Public defenders often know this law very well also and deal with it on a regular basis. Defending these cases makes a lawyer feel like an American.