Will this install directly into my door without modification?

Yes. This assembly mounts at the factory attachment points inside your door panel. No drilling, welding, or custom brackets needed — unbolt the old unit, bolt this one in, and reconnect the electrical connector.

Do I need any fasteners that aren't included?

The assembly comes complete. Use the factory bolts from your original unit — they'll thread directly into the new regulator mounting tabs. No additional hardware required.

What if one of my windows is stuck — do I need to replace both sides?

This unit is sold individually for one door. If only one window is failing, buy one assembly. If both windows need repair, order two units — one for each door.