my daughter is 16 months old and was also a preemie. she was born 8 weeks early and was only 2 lb 1 1/2 oz when born and was in NICU 6 weeks. she had no major complications and is now 20 lbs! so, if you ever have an preemie questions, feel free to ask me! :)
as for the sleeping.......i would say that our daughter did sleep alot. in fact, i think we were pretty lucky as far as her sleeping through the night. after a couple months, she was almost sleeping through and only got up because we had to wake her up once during the night to give her medicine for her acid reflux. during the day, she did sleep alot but was also up often because we actually had to stay on a feeding schedule so she could gain weight. during the 6 weeks she was in the hospital, she did seem to sleep alot but the nurses always said that was a good thing because they grow in their sleep and she had a lot of growing to do. :) so, i think definitely mention to your pediatrician your concerns but unless your pediatrician is concerned, it is probably fine.
congrats! :)