Reis, the term "insert" would refer top a factory built fireplace. This one apears to be a masonry fireplace built on-site which would not make it an insert.

If you see any gaps inside the firebox area and above that will not keep the fire in the fireplace, then you are right to call for servicing by a qualified chimney pro (Level II inspection).

All you have to do is find one thing wrong in a fireplace to justify a call for evaluation and all repairs as needed. The NFPA also calls for all fireplaces to be inspected by a fireplace pro when a house transaction takes place.