So far, the most urgent needs are
Running Back
Middle Linebacker
DBack
Defensive Tackle
I think the way you have to look at it is that RB seems to be the one position that can definitely be filled in the 2nd round. That means that you have to take Dback, DT or MLB in 1st. If Patrick Willis or Okoye is there, enough said. If they are not, you take one of the two DBs that are rated highest. The one big decision is wether or not they spend a 1st on Okoye. If he is there, it is definitely a possibility. If not, the answers are above.
In the end, I believe it comes down to Okoye, Willis or DB depending on who is available. No trade ups or down.