@Pablo888
All you really need is a CRECI licensed real estate broker - WHO IS EXPERIENCED WITH INTERNATIONAL BUYERS. If he/she commits to carry out the complete process ending up with the escritura, then you do not need an attorney.
This broker is paid by the seller, and may charge the buyer a little fee (R$1000-2000 for example, probably depending on the commission he is earning and how hard you push him), to do this work.
Otherwise you will need to pay for an attorney (who will charge more), as it is impossible for a first-time international buyer to understand the process, let alone actually be able to complete it...
In either case you need to verify with them that the property is able to be sold, the documents and taxes are up to date, etc.