I am still trying to determine where a package would install when I pull it down or manully install it.
It depends on what package it is. One thing you can count on ... APT will put it where it belongs according to the FHS. If you want to know where it installed a package, ... $ whereis packagename
As far as the flash plugin goes, my experience is that it installs automatically, but like all informed hobbyists, I use Etch. I'm sure HappyTux's suggestion will work. If you can't do it right, tho, unpack the file you dl'd from Macromedia, then navigate down to a plugins directory in .mozilla, and put the files from the Macromedia package in it.
Of course that will only work for a 32-bit system.