You should hire an attorney for your preliminary hearing in Pennsylvania.
A preliminary hearing is an early step of the Pennsylvania criminal process. It is an incredibly important step in the process. What happens at the preliminary hearing can impact the entire rest of the case.
The best-case scenario at a preliminary hearing, is that the charges of the case can be withdrawn or dismissed, or for, say, various reasons, be it dismissed for lack of evidence, dismissed for lack of prosecution, charges themselves can be dismissed, if not the entire case. For example, an experienced attorney can try to get felony charges dismissed where perhaps only misdemeanor charges would be held for a court that could put a defendant in a much better position moving forward.
Having an experienced criminal defense attorney will be able to help both get the best possible outcome at a preliminary hearing, and as importantly, they'll be able to set the stage if the case were to go forward, or if charges were to be held for court by their actions and, say, the testimony at the preliminary hearing. Having them in your corner from as early as possible in the process at the stage of the preliminary hearing is incredibly important, and they should be involved as early as possible.