
Thanks to research on the board and some PM encouragement from Injundon, I decided to go for it and did my own installation of a new head unit and 4 speakers in my 2008 base model. All went well.
I installed a Pioneer DH5000 UB from Crutchfield and it sounds excellent. I noticed the upgrade right away even before I replaced the speakers. It's amazing to have a USB input and to put my tunes on an 8 gb thumb drive in the glovebox and not have to worry about CDs. I rip my music for high quality and it sounds great. Almost as good as the CD player and much, much better than playing an analog signal out of the headphone jack on my MP3 player in the AUX.
I found the combination of directions from Crutchfield, Metra (for the dash kit) and the MusicLink directions I found on here somewhere to be pretty sufficient to guide me through my first install. The hardest part was getting to the 2 8mm screws that are way up inside the center console, mainly because they're hard to see. Like others have said, it takes some yanking to get the console out and clips went flying everywhere. A couple of them got pretty mangled and I decided just to get a new set from Honda. Make sure you shove the clips on really far so they'll hold properly.
No problems at all with the single DIN Metra kit. I tried it a couple ways and used the front DIN install with the trim piece that came with the deck, instead of using the trim from the kit. It's just a matter of personal preference I think. I like having the extra storage pocket in the dash now too.
The Pioneer deck looks great in this car. If you like major bling, this probably isn't the deck for you, but it has a very clean and uncluttered look and blue display works really well with the rest of the dash.
I went with 4 Infinity Reference speakers and the install was no problem at all. I used the trim removal tool that Crutchfield recommended which was very helpful. It was pretty amazing to compare the stock speakers with the new ones in terms of materials and weight.
And, of course, it sounds excellent!
So the moral of this story is: do the install yourself and spend the extra money on the good stuff.
Here are some pics as promised.