cath29... I'm sorry to hear that you've got this added worry on top of everything else.
I am another one of the handful of MNers who had full-blown placenta praevia.
However please try not to worry for now. At your stage of pg this is incredibly common. It is so common that at my hospital they didn't even flag it up to women at the 20-week scan because there was so low a chance of it turning into a problem. The best way that this was described to me is to imagine your placenta like a sticking plaster stuck onto the outside of a balloon (near the hole). The balloon is your uterus and the hole is... well, you can guess. Anyway, when the balloon is deflated, the plaster is near or even partly over the hole, but as you inflate the balloon (as your uterus grows)the balloon stretches and the plaster appears to move away from the hole. This is why so many placentas appear low when the uterus is 'deflated', but as it expands they move right out of the way.
As I said, I did have pp with my first pregnancy. When I was scanned with dd2 I refused to move off the scan table till they told me where my placenta was! It turned out it was low again, but not covering the cervix, and sure enough by 34 weeks it had moved. I didn't particularly take it easy with dd2 (was hard with dd1, who was under 2 when dd2 was born) and I worked right up until a week before the birth. However, I was aware of the situation and that made me feel safer.
Please try not to worry. This is extremely common and there is every chance that you'll have a totally 'normal' pregnancy and birth.
Just bear one thing in mind... If you do have any bleeding - however slight - go straight to the hospital. Don't hesitate - take your dd with you if necessary. It is very rare for the placenta to come away completely, but if it does it is serious (for obvious reasons), so don't feel you are making a fuss or anything, just go straight in. (Bleeding is more likely to happen from 28 weeks onwards, apparently.)
I'm not sure about the D&C/caesarean thing. (Someone else will know if it's true.) I had a D&C before I had dd1, but by the time I had dd2 I'd had a D&C AND a caesarean, and that time the placenta moved and I had a natural delivery.
If your placenta doesn't move (and I'm willing to bet that it will) you will need to plan for an elective section. I'm not sure if Moomin's case is typical and they keep you in hospital from 34 weeks as a precaution in all cases. (I was one of the few who did bleed - quite heavily - from about 27 weeks on. But I promise you that it is very very rare... in the hospital they told me that they get less than a case a year like mine.... So nice to be a medical anomaly !)
Moomin... LOL at 'Tantrums and Tiaras'... you must be my alter ego.
And, cath29, I know I'm going to sound like a stuck record, but please don't worry. Go on as normal (yes, avoid heavy lifting and stuff, but try to be as normal as possible, within reason) and I'm sure that you'll be fine.