My Ati 9800 Fan started to wobble and through heat, damaged the (not
overclocked)card. My computer was brought in to Future shop for repair
under warranty four months ago.  After "repair" my fan didn't buzz and
groan, but the card still has signs of damage; an inability to render
large amounts of transparency like it used to.  And if I try, I either
get 0.1 to 1 fps or severe artifacting, depending on the game.  When
new, the card WAS invincible.

Has my overheated card damaged another part of my machine somehow, or
has Future shop ripped me off by not replacing the damaged card and
just putting a new fan in?

Now that I've waited four months, can I take any action?

A bit late but whenever i take a part in for warranty i write down all
the identifying numbers on it before I do so , this way I indeed
caught several 'repairs' for being nothing but scams

As for your problem , check your bill and see if by any chance the
serial number of the card is on there (or maybe you have the box
still) check if the serial number on the card is different if it is
not you can be fairly sure they only replaced the fan , if it is then
your card was indeed replaced , all you can do after that is check
when the card was sold (you will have to contact ATI for that and give
them the serial number) that way you can track if the card was new
when it went in your machine
If it isn't you have cause to go back to future computer otherwise
there is nothing you can do