Have no hot water (GAS), and tank leaking. I have attached a hose to the drain and have it draining - am still using cold water, which goes back into hot water tank. Plumbing pipes are 45 years old. Hot water tank was replaced about 13 years ago.
Please give me instructions on how to replace the hot water heater myself. Any help is greatly appreciated. I know I should call a professional, but, it's next to impossible - old houses are money pits!! and I have someone who is willing to do the work, but, has not done it before. Please help!!

Start by confirming that you can stop all water by closing your main. Then How to Replace a Gas Water Heater : How-To : DIY Network