Water heater: replace tank with tankless?

I have a 50 gallon, natural gas, Rheem power vent water heater. It started leaking after 8 years, so I need to replace it.

My initial thought was to get the same one and just swap it out, but it’s kind of too expensive to have such a short lifespan.

The picture shows my current setup. How difficult would it be to switch to a tankless design? What natural gas tankless makes/models would you recommend?