I am sure you can find them all over everywhere, but you sound like you haven't done this before. Neither had I, until about a week ago.
I order from
www.crutchfield.com because they will answer install support questions for customers and they provide "master sheets" for your car when you buy speakers or a receiver from them. Those are just basically instructions for getting to and replacing front/rear speakers and the head unit, which are specific to your vehicle/year-range.
With their master sheet, I was able to install speakers in my rear deck back in '03, even though I was clueless on how to do it before I read those instructions. I just used one again to remove those speakers, put them in the doors, and remove the factory head unit and install the one I got from them. I used external amps, so I didn't need to wire the new head unit to the factory speaker wires at all. Just had to run an RCA and a turn on lead to the back of the car for my electronic crossover and amps. That cut the head unit wires I needed to splice into the wiring harness I got by about 2/3.
Of course, Crutchfield is usually pretty expensive. They are authorized internet sellers, meaning you actually get a warranty, but (probably) for that reason they sell for essentially full retail most of the time. You know, the same as a Best Buy or Circuit City or something. Key point: "most of the time". I got this head unit from, which is $170 - $150 at all my local stores that sell Clarion:
http://www.crutchfield.com/App/Product/Item/Main.aspx?g=300&i=020DXZ475&tp=5684
I can't find it anywhere else for close to $90. Especially since the shipping was free on my order and there was no sales tax. You probably want a different head unit, but the point I am getting at is that they have good prices on certain things at certain times. Decent customer service, info on the install process (master sheet), help with the install if you need it (tech support by phone), a warranty (certified internet retailer), and sometimes even good prices. Works for me.
I checked your car there (to the extent I can), and it looks like everything is a "modified fit". Which turns out to mean that they sell you a bracket for $20 that you need to drill 4 holes in your dash in order to mount. I would think this is the kit you are referring to, and you can get it from them. Instead, I would look at exactly what they call it, and then just google for it to find it somewhere else - if that's really all you need to do it yourself. I needed more help getting to the stuff in my car, as I hadn't done it before.
Even if you don't want to buy from them, just go there and pick your car when look at receivers, add a receiver to your cart, and then take a look at the stuff they want you to get as far as wiring harnesses, tools, and adapters. At that point, you will at least know what you will need as far as those items go, if not where all the stupid plastic clips are that hold everything on and such for removal/install of the old/new head unit.
Once I went through the whole "add to cart" thing there, I figured the price on that deck was good enough to cover the bit extra I was paying for the wiring harness, so I bought from them. I have bought from them before too, but way back. They have been good to me, from a customer service stand point. Again, get something being discounted if you get any thing from them, as the regular prices can be as bad as a Circuit City or a Best Buy.
Any way, it looks easy enough for your car, just that extra adapter/bracket (vs my car) so you can use typical DIN receivers. Well, as far as I can tell.
Good luck!