If you have Peyton Manning
, make the trade. You'll get short-term help with Warner or Rattay, and could draft long-term help or shore up another position with the #1.
If you have Eli Manning, don't make it. Plummer will put up some big numbers--if inconsistent ones, and should be starting ahead of Eli this season.
EDIT: Why would you want to draft a QB #1 overall, anyway? Do you start multiple QBs? Peyton Manning will be your regular starter for another decade.