I just looked up how to do replace the inner planum thing. Looks like a 45min job if you're handy. Honestly I'd just pay the service center to do this job for $58. I wouldn't do this for less than $200 myself.
1 Remove the rear underhood apron. See
Underhood Apron - Rear (Remove and Replace).
2 Remove the outer HVAC plenum. See
Duct - HVAC Plenum - Outer (Remove and Replace).
3 Remove the hood latch cover. See
Cover - Hood Latch (Remove and Replace).
4 Remove the underhood storage unit. See
Underhood Storage Unit (Remove and Replace).
5 Remove the LH and RH wiper arms. See
Wiper Arms (Remove and Replace).
6 Remove the LH and RH shock tower cover. See
Cover - Shock Tower - LH (Remove and Replace).
7 Remove the cowl screen panel. See
Panel - Cowl Screen (Remove and Replace).
View attachment 563111
8 Release the clips that attach the inner HVAC plenum, and then remove the inner HVAC plenum from the vehicle.
View attachment 563110