Question about abdominal aortic aneurysms and surgery. How massive is the scar and surgery?

AAA surgery. AAA surgery is a big one and most doctors need a large scar on the abdomen. There are a few doctors doing them from within the blood vessels but most open the abdomen. Each aneurysm is different and some take longer to do than others. You should ask your surgeon how long your surgery would take. Even if the scar is really long, it's better than dropping dead suddenly from a ruptured one!
Varies. Until recently, a large surgery with a long abdominal scar was always necessary. Today, some aneurysms can be repaired via a puncture wound in the groin by "unfurling" a flexible liner inside the aneurysm to reinforce it and reduce its diameter. Have a frank conversation with a board-certified vascular surgeon but do not avoid addressing this very serious problem because of the scar!
Many options. There are a variety of new options which have expanded the number of approaches with some minimally invasive techniques using an endovascular approach with some stents for limited aneurysms not involving the renal arteries.
Not massive. Most of the time if an aneurysm can be repaired with an endograft the incisions are small and in the groin. If it needs to be repaired traditionally then the incision is larger and is located in the midline of the abdomen.