337 for interior plastic

So, I sent off for new interior plastic. The pieces are not PMA'd so
the dealer is telling me I need to do a 337. Reading part 43 I see
preventative maint says..

(9) Refinishing decorative coating of fuselage, balloon baskets,
wings tail^
M
group surfaces (excluding balanced control surfaces), fairings,
cowlings,^M
landing gear, cabin, or cockpit interior when removal or disassembly
of any^M
primary structure or operating system is not required.^M


This makes me think I can replace my cabin vent covers myself. Does
that means I can also sign the 337? Do I need to pay an A&P a minimum 1
hour labor to sign the 337?


-Robert