Officially, you can change a selection up to 7 days before the contest date if you notify the event chair IN WRITING.

SHOULD you do it is a different question.
I changed a song 2 weeks before UIL one year. I can't remember what song just wasn't clicking with my band, but Two British Folk Songs was a perfect fit, and we were ready in time for UIL.

I would suggest go ahead a read a new song or two, and see which one resonates with your band. If they latch on better to a new tune than the original one you submitted, keep the new song and send in the letter. If not, power through. They might surprise you.

Either way, best wishes.