@annie1 , although I am a male, I was informed that the front (Anterior) entrance is similar to a caesarean section. I can't judge, but I can state that the scar is not insignificant.
My first 4-to-5 weeks post surgery was challenging due to the sliced stomach muscles. You're right that we use these muscles without cognition, and when they can't be used, you definitely notice. Simple movement including walking, engages these muscles, which do not want to be engaged over the first few weeks. But now, 6 weeks later, I am exercising them with minimal pain.
My back muscles are also sore, with notable irritation to mild pain on one side (RHS) more that the other. These scars, L and R of the spine, are the access points for the pedicle screws and the two rods.
Having multiple levels done simultaneously will naturally increase the risk, but the surgeons know what they are doing, so surgery risk is mostly mitigated. Unfortunately, fusing multiple levels does translate to a more challenging recovery in terms of BLT and your overall body's accepteance of the new hardware.
My surgery was conducted at a Private Hospital in Perth, Australia, by a neuro-surgeon who belongs to the Spine Institute here, and has operated on my spine previously (an emergency bi-lateral microdisctectomy when I was paralysed R-leg).