I have done this and you all are right you have to find the right sized head unit...I also use the Pioneer brand the unit I have is about a 1/4 of a inch too long but I have learned to live with it plus there's things that could be done but I haven't yet or not sure that I will...like for instance I could make a trim/bezel for it to make it look more stock or I could shave out some of the dash or cubby hole space at the headunit...right now I have just been living with it but the trade off is now I have touch screen IPhone/Andriod Auto, Bluetooth, Navigation, XM radio, Pandora, HD Radio and a backup camera!!! flips ups are nice too but tend to get in the way of things...here are some pics of my at DIY install although I am sure Bestbuy or a Tuner Shop would probably do a cleaner install....
These are all of the pics I could find now but I could post more up close when I get home this evening if you like.