Shop says manifold must be removed to replace a sensor for $612. Reasonable? on 2001 Toyota Sienna

They say "Won't pass smog test if check engine light is on"

Asked by for the 2001 Toyota Sienna
sounds like a knock sensor issue to me. yes it does have to comr off,if you have 2 knock sensors repl both while there and ck wiring also
I guess the price is OK, then. I appreciate your help.