The final bit of information revealed, concerning a census carried out by David, contains 5 points of contention. All 5 supposed "contradictions" are discussed below.
God allows Samuel to mourn for Saul for a little while, but eventually, God tells Samuel it's time to move on. When we lose friends because we have chosen to follow God, He will bring us into the fellowship of people following the same path.
How poetic is it that as Saul is confusedly searching for Samuel to assist in finding donkeys, Samuel is watching Saul and being told by God that this is Israel's king?