First of all, it is not uncommon for them to spend a great deal of time sleeping in the first hours and days. It may be tomorrow before the baby starts to feed more normally.
Second, the brown stuff you are describing is likely just undigested amniotic fluid
. It would be worthwile mentioning this to your nurse (hopefully you delivered in a hospital?) so that they can also confirm that this is likely normal.
I hope that this helps! Good luck!