I wouldn't worry at all about your undergraduate GPA and Texas Tech. First of all, the GPA trend (better the later half of school) is fantastic and, most importantly, the Adcoms are much more concerned with what you accomplished professionally. The GPA and GMAT are just data points to make sure you have the raw brain power to do the work and (your 700 will alleviate any concerns that an Adcom could have in this area).

It is nearly impossible for any responsible consultant to tell you to aim for top five. The top 5 schools are incredibly competitive and not even the most qualified candidate is guaranteed. But, with that in mind, I think that you should absolutely aim for the top 15 schools (I say this because schools tend to rotate in and out of a top 10, but, normally the top 15 stay consistent - schools like Tuck, Duke and NYU could be good options for you). Recommendation letters are a key component for top tier schools so I would give these a great deal of thought and pick recommenders who will sing your praises. Having a compelling story (good essays) is also important.

If you are sure that you want to attend business school next year, you should also apply to one "safer" school. Even with strong experience, a good GMAT and fantastic recommendations, you won't be a shoe-in for a top 15.

And, no, I don't think it is necessary to retake your GMAT. I hope this helps!