You can do it. Just wait till the weekend or in the evening so then you won't find the parts and you'll be without hot water for a few days and your wife will have kicked your rear. lol
I'd suggest going to Ace or a plumbing supply somewhere and have the new diptube ready to go. It slips in the hole under the cold water inlet. Shut off the water to the house first. Depending upon the type, you have to remove the nipple and some may be under a nut that takes a socket to remove it.
Definitely unhook the hot water line also and consider unhooking the gas line too. Have a helper. Sometimes the nipples can be so tight the whole water heater will move before the nipple does. You may need a cheater pipe and/or a hammer to knock it loose while someone else is holding down the water heater. Be ready to replace the nipple that may get burgered up with the pipe wrench. Use thread tape on the threads.
If your hot water heater is past its guaranteed life of 6 to 10 years, then consider a new one. Get an estimate for your local plumber for doing it. One that handles your brand may still get you a free diptube replacement.