Well, as far as I know, that Rio is just a slightly restyled 3rd gen Hyundai Accent so you might want to check out
my worklog.
As for the screen, you're not going to get a full fill of the DIN area like in your mockup. Check out some of the DIN conversion kits for the 7" screens and they all have some bezel. An 8", like I have, is closer but you may end up doing some fabrication to make it fit.
Check out where the clips and such are behind the bezel to be sure you have room for the CD and button relocates. You may not be able to clip your bezel back on depending on where the clips are.
Give a holler if you need a hand. Your Rio might be close enough to my Accent that I could help.