Well - I finished the dress, after several attempts and lots of pulling-back! I don't think she'll be getting a change of clothes any time in the near future!
I think it turned out quite well, though my finger may never recover from those VERY pointy little needles!
I made her a little flowery headband too, which was fiddly but effective.
I decided against the sleeves:
a) they looked fiddly to make as well as sew-in
b) I thought they would be difficult if a child was trying to put the dress on (or off) the doll.