Hi all,
For anyone who is interested, I got a bit of clarification on this issue of whether or not an agent is needed to transport your pet. Below see a note from the people at Latam Pet Transport (who have been very responsive thus far). They also mentioned that the cargo option is significanty more expensive. A while back I was quoted 1600 USD from another carrier (this included airfare) for cargo transport (verus like $350 USD for the excess luggage price).
There are 2 flight modalities, cargo and excess baggage. On the first modality you don´t need to be on the same flight, the check in has to be done at the cargo terminal of the airport and a broker has to do it (us, not the owner). On the second modality you travel on the same flight, with your pet as excess luggage and you have to inform the airline you will be travelling with your pet when you purchase the ticket. The airline will charge you for every kg your pet (+ crate) weights when you do your own check in at the passenger terminal.