To sum my post up, Quadro cards are for 3D rendering and Geforce cards are for gaming.
In terms of hardware the Quadro Fx 3500 dose seem similar to the 7900 series BUT the software is completly different. Gforce uses DX and Quadro uses OpenGL/CL. Using your Quadro could have a number of different results from giving you performance on par to a 7900 (Id say youd be lucky), to playable but with major artifacts, to the game not even starting. Since you already have the Quadro you can try it out, wont hirt anything, but im just saying right off the bat: dont expect very much.