It is not expensive.
Atwood water heater tank cracked.
One of the primary issues with older water heaters is the buildup of sediment caused by natural minerals in the water.
I d replace the water heater.
Trailer life and motorhome magazines bob livingston and bill gehr show you how to replace the inner tank of a leaky atwood rv water heater.
When i first put a hole in mine i looked for a replacement and was floored at the cost.
New seal rings gaskets kit available atwood 96010 should come with new tank if that is way you go.
These minerals calcify and form deposits inside your water heater which eventually causes enough stress to crack it.
I called a couple welding shops and was quoted 20 to patch the screw hole a crack might be 40.
The pic in your signature suggests that there are more than 2 of you so i d upgrade to a 10 gallon if there was room for it to fit.
All atwood tanks are aluminum and can be welded if cracked leaking hopefully with tank still attached to front of water heater drawn pan etc if tank needs to be separated from drawn pan etc then the seal rings around combustion chamber and exhaust port have to be cut off t p relief valve removed old version uses 1 2 style.