Hi,
This information is a bit late for plp76, but might be useful for others looking for the same service. We did a similiar cruise stopover in Rio and used Rio Airport Transfer who provided us with a taxi transfer service from our cruise ship to hotel and from there to the airport - Tom Jobim or Galeao, I forget which. The day we arrived in Rio it was very hot so it was a relief to be transported in a car that had air conditioning, which the cheaper yellow cabs don't have.
We also caught a yellow taxi from one of the malls back to our hotel and the driver was quite exuberant, to put it nicely, whereas the drivers from Rio Airport Transfer were a lot calmer drivers and felt a lot safer. So I would suggest booking with one of the nicer companies, as suggested below. Our experience with Rio Airport Transfer was very good, but I'm sure there are other companies that offer equally as good taxi transfer services.
Regards
Rick
Rio airport taxi transfer website is www.rioairporttransfer.com