Another way to do this (if you've ever considered it)

Cut speaker holes in that bottom 'kick' panel thing
and install a set there.  Has two plusses.. extra
sound up front.. and a nice big honkin hole to get
the power winder motor out every now and then ;-)

Otherwise.. start a wrasslin! (not fun)
good luck!

mine did the same thing.. pulled it out and de-sludged
it (all the crap dirt, water etc: goes down there and builds
up in the motor over time)  Started working again, although
within 6 months or so.. it lost it's oommmph.

I have a brand new one in a box ready to go when it
finally dies.. but will have to switch the wire harness
over.