Hi karan812,
First off, a 700 is an outstanding score (it's just a bit below the 90th percentile overall), so it could be enough to get you into your first-choice School. As such, a retest might not be necessary. A Q45 won't impress anyone though, so I understand why you want to improve that Scaled Score. Depending on the Schools that you plan to apply to, you would likely find it beneficial to speak with an Admissions Expert about your overall profile. There's a Forum full of them here:
ask-admission-consultants-124/With your Quant and Verbal Scaled Scores, you're already a strong logical thinker - so however you choose to proceed, your emphasis should be on Tactics and pattern-matching. The Q45 means that you were really good on the 'math' questions that you faced, but you missed out on lots of 'strategy-based' points.
1) How many hours do you think you can study each week going forward?
GMAT assassins aren't born, they're made,
Rich