Replacing reliance gas hot water tank -- any experience/advice?

Our home came with a natural gas hot water tank rental from Reliance which is only 5 years old. Its having some issues and I'm thinking this might give an opportunity for us to get out of our Reliance contract as of course they are notoriously bad from a financial perspective.

Has anyone dealt with this scenario with Reliance? What was your experience?

Did you replace with a tankless or regular model? Did you buy your replacement yourself individually or did you simply pay an installer to do the whole thing ? What brand/model unit did you choose?

Did you call a plumber or HVAC company to do the swap? Who or what company would you recommend?