Installing a water heater is not all that complicated, but there are some things to consider. First, you have to remove and dispose of the old one. Depending on where you live, that may be easy or it may be difficult. Second, you have to get the new heater home and into the house. A tank is not gosh awful heavy, but they are a bit awkward to handle, and you sure don't want to drop it. As far a the disconnecting and connecting is concerned, it's pretty straight forward so long as the new vent matches the old or the modification is simple. If I were doing it, I'd install new copper flex lines for intake and output with diaelectric nipples into the tank. I also use a new TP valve. The gas is connected with a flex line already and that can be reused. You will need a pipe wrench (two would be better) for installing the nipples, a can of pipe sealing paste or a roll of teflon tape, channel lock plier or a large adjustable wrench for the gas fitting, removing the old TP valve, and copper flex pipes, and some liquid dish soap for testing the gas connection. Fill the tank completely before turning on the gas and ignition (electronic or pilot) To do this, open a hot water faucet, turn the water supply on. When the tank is full, the water will run out of the faucet. Test the gas fitting before lighting the burner with the soap. Any bubbles indicates a leak. Of course, check the water fittings for sign of leaks, too. That's about it.