Hi, I had to junk my pool heater last year. Jandy/Laars 400,000 BTU. I should have junked it sooner as it seems the copper tubing was disintegrating which caused copper staining in my plaster. Anyway, I'm looking for another heater to last another 10 years or more, 400,000 BTU's. My pool is an inground chlorinated gunite, 27,000 gal, 3M quartz plaster. My wife likes to keep it at spa temps, at least 90+ degrees. I had a LoNox natural gas unit. I will be installing it myself. I'm not concerned about the plumbing. Maybe a little concerned about the wiring. And wondering if any gas pressure testing equipment will be needed when installing the new unit. I can't afford top of the line. Just looking for something mid-range, easy to install, and weather proof as it will be exposed. Is it safe to buy on Amazon or Ebay? Any suggestions would be greatly appreciated.