OEM Radio question

The important question will be the wiring behind the radio deck. The mp3 functionality is handled by the stereo itself and shouldn't be the reason for any wiring changes, unless speaker numbers wattage etc. are different. Are you able to pry open your 2005 stereo out of the dash? If so, you can easily check the difference.
If not, take measurements as much as you can on the front side, just so you the dimensions match. In your shoes, I'll get the 2006 radio from the scrapyard and take it to any credible audio guys around. Have them test if all the features work, before delving into the swap.

Sorry for the general type answer. I don't have the detailed knowledge on 2005 vs 2006.

PS. I have a bad habit of advising even when not asked. So here's my $0.02. You know, the mp3 capable CD playing ability is an attractive feature to have but you will very soon get over the added hassles of cutting mp3 CD's and the associated CD skips and jumps. The world has moved to bluetooth, internet audio and flash drives. Those are going to be aftermarket only features, but will perhaps give you a longer satisfaction period. If the 2006 OEM radio gives you the capability to play flash drives or auxiliary port, I would jump on it. If not, I will think again. There is an added question of how long do you intend to keep your 10-11 year old vehicle. I have had no problem hanging on to mine for good 15 years. If you are thinking of getting a newer vehicle soon, I would hold my nose.