Yes to so much of what has been said on here!
Definitely cotton pants rather than mesh ones, I got some giant M&S rejects six, count 'em, six sizes above my normal size and they were an absolute lifesaver, not least because I was still wearing them several weeks after the operation. It took a good month before I could wear clothes that pushed on the scar at all, if not longer.
Also a big yes for arnica. But don't just take the normal tablets from Boots. I was recommended to get the super-dooper 200c arnica from Helios.co.uk, to take in the couple of days running up to the op and the few days after, and I did have spectacularly good healing - even the midwives kept commenting - and was up and about quite quickly.
Also yes to anything that keeps your bowels going - I used to get DH to bring in those litre packs of Innocent smoothies and drink one every day while I was in hospital. Food generally is a good thing, hospital food is grossly unappealing, and you get hungry at odd times of day (at least I did).
Another good trick when you get home is lavender and tea tree oil in the bath - I did this every time my scar started twinging slightly, and it really helped.
And finally, a friend packaged me up a small selection of toiletries deluxe, which was such a lovely treat when I staggered down the corridor for my first shower. If you're going to be there a few days, it really helps you to stay human. I also found under eye concealer to be essential, but that might just be me...
Good luck - I found it far less of an ordeal afterwards than everyone said it would be, so I hope it is as good for you.