Does this mirror bolt straight to my truck without any modification?

Yes — it mounts at factory rocker points with no drilling or welding. You'll use the existing holes on your truck.

How stable is the mirror at highway speeds when fully extended?

Manual mirrors are solid once locked in position. The lever mechanism holds the mirror arm firmly in place — no vibration or drift under normal driving conditions.

Can I adjust this mirror while I'm driving or does it need to stop?

The manual lever is accessible from inside the truck, so you can make small adjustments on the move. For major repositioning, pull over and lock it in place before hitting the road.