I had ELCS - very calm, very painfree, very enjoyable!
You have a small local anaesthetic (for me, less scary than anything I've had at the dentist) before they give you a spinal or an epidural - which takes effect very quickly, a bit like your leg going to sleep, but over a wider area - I got an odd tingly feeling in my back for a moment when the spinal 1st went in, which was strange, but not painful.
They take a LOT of trouble to be sure the anaesthetic has done the job, running ice cubes over you until they are sure you can't feel anything (remember with an ELCS, they aren't rushing to get a baby out, so it's all very calm) -
I had no pain at all during the op - I could feel some tugging and pulling, a bit as if someone was leaning on my belly or legs, but it wasn't painful at all.
My scar never hurt, although by day 5, which is when they took the stitches out, they had started to pull at either end of the scar as it healed, and that was irritating.
Once I had the stitches out, it really felt okay.
The scar is about 13 cm long ( I just measured it) - it's a thin purple line which you can barely see underneath my pubes. I had the op 8 months ago. I don't really have an overhang, which I think some people get - I think that's luck of the draw, I never got any stretch marks when I was pregnant either, I don't know why.
The only pain I had was when an unpleasant midwife (who was very sniffy and eyerolling about my C section) didn't give me the right painkillers the day afterwards, so I missed a dose of the stronger ones, and had to have a tramadol to get on top of things again.
Thereafter I was on paracetamol and voltarol, which totally did the job.
I'd recommend that you (a) stay on top of the painkillers - ask beforehand what you will get and when you need to take them, as they keep inflammation down as well as get rid of pain (b)shave or immac your top bit of pubic hair yourself, so it's neat and they don't have to do it for you, and (c), unless you are happy with it, ask them if you can be catheterised after they've put your spinal or epidural in, and after they've got the screen up across your body. Then you can't feel it and aren't aware of it. (catheter came out painlessly about 14 hours after my op - I thought I would hate having it in, as it turned out I barely noticed. And after weeks of night time toilet trips in late pregnancy, I quite liked not having to get up!)
It is major surgery, but it's very routine, too. ELCS's are very different to EMCS's. You won't be exhausted, for a start.