Is surgical ablation something they have to open your chest for (vs by catheter)?

Sort Of... The answer used to be "yes." in recent years, they have some minimally invasive ways by which they can do "mini maze" procedures and other interventions through small incisions in the chest.
Usually. Assuming you are asking about atrial fibrillation ablation - the surgical technique either requires a sternotomy (open chest) for the typical maze procedure, or through smaller incisions in the chest wall (minimally invasive maze). Both are more invasive than the catheter ablation technique, which only requires needle punctures.