Definitely talk to your agent first. ask him or her to please contact the Seller's Agent and explain the situation, and ask for the fix to be completed. In the meantime, ask your agent to get you all the paperwork that you need hsowing the Seller had promised the fix in the contract. Then review it again to make sure you didn't misunderstand the language (yes, sometimes misunderstandings occur).
Lastly, if the Seller and/or her agent refuse to help, let them know that you will need to mediate first, then you fully plan to take them to court for the repairs as well as any other damages that may have been incurred. If that still doesn't do the trick, you will need to follow through.
In Colorado, under $7500 damage, the case is to be heard in Small Claims Court, where you cannot have an attorney, so make sure you have all your ducks in a row. I would be willing to bet that you won't get that far, but regardless, best of luck to you!