Trying to simplify for the next guy that's learning as he goes like me. No extra parts removed for this thermostat replacement.
1. First things first, raise the car, the higher the better.
2. Drain the radiator fluid completely.
3. Remove the lower radiator hose at the connection to the radiator by removing the spring hose clamp. (Leave the other end of the hose clamp connected to the thermostat cover to make for easier reinstallation.)
4. Remove the thermostat cover located at the other end of the lower radiator hose where the hose connects to the engine. You'll need a 10mm ratchet. This is where it gets fun. Hopefully you have an assortment of ratchet attachments to make for easy removal of the two 10mm bolts that hold the cover in place. If not, you'll have to do your best with the bolt removal. You can get a clear view of these bolts at two different viewing angles from under the car. Just follow the lower radiator hose and you'll see the lower one first. To see the second one, look from the next viewing hole closer to the firewall.(When you remove these bolts, about a cup of coolant with pour out so watch out)
5. Once you remove the cover, just pop out the thermostat.(Chances are it's been there for a while and it won't just pop out easily, you will have to use force or pry it out gently. More fluid will come out) At this point you can simply press the hose out of your work area without removing it.
6. Place a gasket on your new thermostat making sure the gasket is seated tightly around the edge.(Oem gasket will have a "bump" of rubber poking out. Place this bump just above the pressure pin hole to ensure that the pin hole is at 12:00. The pin hole is a small hole in the thermostat plate that has a pressure relief pin. MISHIMOTO GASKET DOES NOT HAVE THE EXTRA ALIGNMENT PORTION OF THE GASKET LIKE THE OEM GASKET HAS. So, I recommend ordering a new oem thermostat gasket if you are using an aftermarket racing thermostat.
7. Place the thermostat with the gasket bump facing up and look to verify that it is seated properly in the notch that mates with the gasket bump.
8. Carefully replace the cover.(Use a second person to apply constant pressure to the hose keeping the cover seated tightly to ensure the thermostat doesn't pop out before you get it screwed in completely.)
9. Replace lower radiator hose connection to the radiator.
10. Refill coolant.
11. Crank car with radiator cap open for about 15 seconds and turn off.
12. Top it off again if it needs it. Perform a pressure test if you can. If not, watch it closely to make sure you don't have leaks.
13. Lastly, Clean the dang thing up and hit the road.-Hope it was helpful.

 

This guide helped me immensely and I wanted to add some pictures to go along with the text as I followed it.

My radiator cracked so I replaced both it and the thermostat as a precautionary measure.

I wasn't about to pay Honda the quoted $700 to do this job I knew I could tackle.

This was done all from under the car. You have room for one arm so don't expect to use both hands. A 2nd person can assist from up top but that's about it.

This is the thermostat housing cover. I used a 3-inch extension and 10mm socket to remove the bottom bolt. (that's the one I already removed here) For the top bolt I used a 6-inch extension and a 10mm deep socket.



This is the thermostat in its housing. Note the bump at the top above the pressure pin. I had to use a screwdriver to pop it out as it would not budge by hand.



I had completely drained the system as much as I could but after I pulled the thermostat all this came out. Thankfully I was wearing safety glasses and positioned myself enough out of the way I didn't get completely drenched.



Once you have the old t-stat out, you need to put the new gasket on. I bought a genuine Honda thermostat and they come with the gasket. One thing I didn't know was that there is a slit the thermostat sits in. Just position it so the bump is directly above the relief pin.



Now that was for me the "easy" part. It's fairly easy to reposition the thermostat and put it back in the housing, but if you touch it at all it will fall back out. There is nothing to really hold it in there. So when putting the lower radiator hose back on, I fought and fought trying to line it back up and not knock the t-stat back out. What I finally had to do was remove the t-stat housing cover from the lower radiator hose and very carefully place it over the t-stat and hold it there while my wife reached down from above and put the top bolt back in. I was able to do the rest myself.

Hope this helps other do-it-yourselfers.

 

Nice...I have not had the pleasure of doing this yet but I assume leaving the radiator hose connected to the thermostat housing makes most of it bareable.