It's not a simple job to change out this one. There's an A7 heat pump on top.
https://ecorenovator.org/forum/showthread.php?t=2286
If I can't stop the leak (cracked tank etc), I'm pretty sure the A7 HX tube will be destroyed trying to remove it.
So, maybe some
https://www.amazon.com/dp/B000KKPFFA J-B Weld 8272 MarineWeld Marine Epoxy will keep me in hot water for another 4 or 5 years.?.