Hi longranger25,
The extra information you've provided is quite helpful - it points out some things that you need to consider IF you're going to keep studying:
1) With a 700/Q50, you have an outstanding GMAT score (right around the 90th percentile overall), so you can comfortably apply to any Business Schools that interest you. As such, retesting is not necessary.
2) If you can finish the entire Quant section in 35 minutes and still score Q50, then you should be able to SLOW DOWN and eliminate any silly mistakes from your work. In this scenario, the 'level' of the question wasn't the problem - you moved too quickly and didn't do enough work to earn the Q51.
3) The bulk of the missing points that you're looking for are going to be found in the Verbal section and they are NOT going to be '700-level' questions. You need a better mastery over Verbal tactics (for RC and CR) and likely a bit more grammar knowledge (and pattern-matching ability) for SCs.
What resources have you studied with?
Why do you think that you need to retest?
GMAT assassins aren't born, they're made,
Rich