Should i wait before installing the rio or is it reletivly easy to add the tuner on after instalation?

Depends on your dash. If it were MY car, no problem, because everything unscrews rather easily without bending or damaging anything. If there's a lot of digging and prying involved in getting the player out of your dash, well, that's something you have to consider and it's up to you. Most dashes, the sled's tabs will bend to connect to the mounting kit, but the mounting kit screws to the dash or frame, so you simply unscrew the mounting kit (leaving the sled attached) so you don't have to bend or pry anything.

edit: it appears riocar.org isnt responding...

Known problem hopefully corrected soon. And yes, this was a FAQ entry which I would have linked you to if riocar.org had been up.