You can also get out the yellow pages, look up plumbing supply, and call around to see who carries Toto in your area. Prices will (like that silly plumber toilet install price) vary considerably for the exact same toilet, so have the model number and color handy.
Also, the Drake II is a GREAT toilet. A more reasonable workhorse version is the original Drake (CST744S at 1.6gpf, or CST744E at 1.28 gpf). Both work well! However, the Drake II comes automatically with CEFIONTECT finish, universal height and the Double Cyclone flush which gives a little better bowl wash, and a more modern look, so you really can't go wrong with it. I have both kinds (regular and double-cyclone) of Toto flush, and like them both, but the double-cyclone is cool.
If you have a standard 12" rough-in (i.e. 12" from the finished wall, not the baseboard if you have one, to the center of the flange; i.e. 12" from the finished wall to the bolts holding your current toilet to the floor), the Drake or Drake II will fit. Also check the position of the water supply -- is it coming out of the wall and at least 5" left of the center of the toilet? If so, you're good to go with the Drake or the Drake II.
$480 installed is pretty good if it includes the Drake II (CST454CEFG) in the price. Just make sure he isn't quoting you the original Drake, CST744S or CST744E. However, if you do it yourself, you will take pride in it and be sure it's right (i.e. no wobble, solid tank install, etc.).
As to the seat, any standard elongated seat will fit on the Drake II -- the seat holes in the porcelain are in a standardized layout. On my two original Drakes, we used a nice Bemis slow-close, wooden seat with quick-disconnect hinges, which everyone seems to like. However, on our Carlyle II, it came with the Toto SS114 slow-close seat, and I have to say that if the Bemis seats ever quit, I would replace them with the SS114. It is plastic, but sturdy and comfortable. The slow-close mechanism is great. (Tell family members to let it drop itself, it wears out faster if you push it down rather than letting it close on its own once you start it.) I was just in a shwanky hotel in another city yesterday, and was pleased to see a Toto Ultramax in the bathroom with the SS114. The toilet was probably 5-6 years old and had the SS114, and looking inside I realized that both the seat and innards of the toilet were original. So in daily hotel use, this thing was still in great shape.
Just as an aside, about 15 months -- and 900 posts -- ago, I was in the same place you are right now -- maybe knew even less. Read this site, decided on a toilet, priced it out locally and online, got stupid quotes from people (hey, it's New York), decided I would see what would be involved doing it myself, looked at this site, looked at some videos, gave it a try. Loved it, and the rest is history.
You will find a few things. If you are taking off an old one, something will be a pain. Flange too low or too high, broken, etc. Something will be a pain to remove. But you will figure it out. Ideally, your flange will be mounted on top of the finished floor. If not, you can use an extra wax ring. Once you get the work area cleaned up, putting in the new thing will be a piece of cake. Your waxless seal is fine, but I have to say wax rings are quite workable, and they are really flexible if your flange isn't mounted on top of the finished floor.
When you mount the tank, read the Toto directions: if you have to try the tightening part a few times, that's what we all do. Put the tank on, hold it with one hand so it's straight, tighten by slowly alternating from side to side, watching the porcelain compress the rubber gasket and that the tank is approaching all three points of contact (you'll see this in the directions) evenly. When they are just about to touch, tighten slowly; about the thickness of a sheet of paper is what you want, once one point of contact touches, stop, as porcelain doesn't compress porcelain -- it cracks. If the others are a sheet of paper or two gap, that's good enough. Check for no wobble. If you need to loosen a bit or a lot then tighten so it's more even, just do it a few times, and you'll be all set.
I would add to your list of stuff to get a new braided water supply; might as well put a new one in now. And use a set of closet bolts that has two nuts and two washers; you put the bolt in where you want it, tighten it down to the flange with the nut and washer, then drop the toilet on and use the second nuts and washers to attach the toilet to the flange. If you have a Dremel (or hacksaw), you can cut the closet bolt to a nice length after installation so the cap fits. If you do, do so before you put the caulk (recommend Polyseamseal) around the base, so the metal dust doesn't get in your new caulk.
And do your actual work when a hardware store or Lowe's is open, just in case you decide that you need something, or drop a bolt down the toilet hole, etc.
I did one toilet, then another, then another. I also rehabbed the remaining 4 toilets in the house with new fill and flush valve, water supplies, etc. Each of those jobs had at least one issue (like I couldn't get the flush valve off, had to cut it with the Dremel, etc.), but the problem-solving is fun!
I will probably replace another one of our old toilets soon.
Good luck, and come back with any more questions!!