Did it say empty the whole tank as part of the service procedure?
For checking the anode rod you only need to drain out a few gallons, enough so when all the water in the pipes upstairs comes down when you take off the anode, it doesn't spill out onto the basement floor.
I suggest letting sediment drain by gravity. Turn off the gas or electricity to the heater. Don't use hot water for several hours. Then turn off the water supply, open a hot water faucet upstairs, and then open the tank drain all the way. Have a big enough bucket so you don't have to stop and start the drain flow several times. You should not need to drain more than five gallons before the water runs clear.
If the manufacturer doesn't have affordable authorized technicians in the area, I doubt if their warranty rules would stand up.
Thanks for the tips.
I am trying to find out exactly what is involved beyond changing the anode and checking for sediment/scale. It says the service has to be carried out in accordance with the company's service and engineering manuals, but I don't see these publicly available.
Another thing I just noticed: the warranty expires if you sell your house! Is that typical?
"This warranty extends only to the first residential purchaser of the TANK and only while the TANK is owned by that purchaser and remains at its original installation site in the United States or Canada. Change in ownership or relocation of the TANK shall terminate this warranty without further notice."