Just do a web search for how to lay sod. I think you'll quickly find
that the right way to do it requires properly preparing the soil. And
just laying new sod on top of whatever is already there isn't one of
the accepted methods. A little work upfront to do it right will avoid
either total failure the first year, or years of trouble ahead.

I'd take pictures of what they do, so when it fails, you have good
evidence of why.