Carlton makes it sound easy but it's not; especially if you don't have small hands.
I did mine today and it took 4 hours from the start of taking the hose away from the inlet to when the system was refilled and primed. I didn't bother to drain the system...I just put a very big bucket under the front of the truck and disconnected the hose and removed it from the inlet. One of the hose clamps was a bugger. Nissan had put it in a position such that I could not get a ratchet on it and had to use a small wrench making abou 1/16 of a turn at a time creating about a 1/2 hour diversion. Once undone I pulled the hose and let the coolent empty. About 90% of the coolant made it into the bucket, which I thought was pretty good. Removing the inlet proved to be tricky. I could get my small ratchet, extension, and socket down in there, but the bolts must have been driven in by a 2 ton ape with a bad attitude! I nearly broke my ratchet on one of them and had to use a deep well socket and an extension to put on the handle so I could get more leverage. Took me about 1/2 hour to get the bolts out. Removing the bolts resulted in about 20 scratches on my arms and a nice big bruise over two of my knuckles...yep; it was a knuckle buster job!
Once the bolts were out I had to figure out a way to get the inlet off becuase it was stuck on there pretty good with the sealant and such. I finally ended up putting the handle end of a screwdriver against the top of it and them used a hammer to tap the other end of the screwdriver and knock the inlet loose. Then I had to pry the old themostat out with a screwdriver because it was sealed in with sealant and corrosion. When it popped out, the top of the engine drained. Scraped the old sealant off, wiped everything up, and put the new thermo in. Put new sealant on the inlet and put it into place and bolted it on. This was definately the easy part and only took a few minutes. BTW, don't buy the sealant from Nissan for $15!!! You can get the Permatex thermostat housing sealer for about $3 at the auto parts store.
Now, before I hooked the lower hose back up I poured a little coolant into it so it wasn't empty and then reconnected it to the inlet and tightened down the clamps being sure to put them in a better position this time so they could be reached with a ratchet and extension!
Once everything is back together you need to fill the radiator and overflow tank. There is an air relief bolt on the intake manifold that you remove first (can't miss it; has a warning about not removing it when engine is hot). Be careful not to lose the little washer down in a crevice in the engine like I did, thank you! Fishing that out was fun! Anyway, you fill the radiator until coolant (50/50 mix) starts to come out of the air relief hole. Then put the bolt back in and tighten snug; but not too much! Then put the radiator cap back on and start the engine. Let it idle until it's up to operating temperature then rev it a few times to get the coolant flowing. Keep an eye on the temp guage to make sure it doesn't overheat! After running for a bit stop the engine and let it cool for awhile. Then carefully open the radiator cap and check the level. Add coolant if necessary and then run again. Repeat until the coolant level stays. Make sure the overflow tank has a proper level too.
That's about it...LOL!
"Every morning when I wake up I know it's not going to get any better 'til I go back to sleep again!" Al Bundy