I am also updating my PS3 for the first time, I finally got internet at my place. I had to update my PS3 firmware first, I am currently downloading the GT5 update, I have lost track, but it is more than 1.00Gb.
I have receive 2 error messages while downloading the GT5 update
(error 80710723) after some research I read that I had to disable Media Server (Under network setting). I have again resumed the download and I am hoping the download finishes today as my net is slow, I have my fingers crossed that the error messages I got don't effect my in-game progress

(I did not do a progress back-up)