If you have never done anything like this before, it will be a bit of a challenge. It'* not impossible though, I've done it, as well as plenty of other members, and we will be more than willing to answer any questions.
I don't know the actual dimensions of the radio compared to the hole for your factory radio so I couldn't tell you whether it will fit or not. You do have one of the big square double din factory radios though don't you? I think I remember the newer Grand Prix having a pretty big radio hole.
COTY - 2012
Tom - 03' Bonneville SSEi', 00' Sierra SLE, 1980 Goldwing GL1100 Interstate