Overseeding with Tall Fescue or MDR ryegrass?

I need to level and overseed my lawn. It’s currently a tall fescue/rye mix. I was going to overseed with tall fescue, but I’m considering MDR instead.
Would mowing low, scarifying, seeding and topdressing with soil be an effective way to introduce MDR, or would I need to kill off the entire lawn and start again?