DH says when you open the tap (after you've turned off the water supply and the pilot light) the entire volume of the water heater should come out. For this reason, one should connect a hose and have a plan for the water that theoretically flows out. A few drips means 1) You're lucky, if you hadn't attached a hose 2) The tap (hose bib) is probably plugged up, which indicates a probable large sediment build up. He says attempts to clear that much sediment are not likely to have a happy outcome.
Watch a few You Tube videos to decide if you can install it together. If you're careful, you could even get it done before the weekend's over. Then you just have to worry about how to get rid of the old one. Hint: In some areas they can be recycled. And yes, code requirements have changed dramatically. Make sure it's correctly strapped in place once it's installed.
We have rental properties, so DH, who is not a plumber, but is handy and smart, routinely replaces the gas water heaters. I ride along to help load the behemoth, but otherwise, he does it all by himself. Also, buy the one with the longest warranty, it's worth the money.