I'm very new to fs but know enough to get in trouble.I've downloaded a 757-200 and installed it in fs2002 and everything works fine except that the cruise speed of this plane is supposed to be approx. 460 and I get an overspeed warning at 350. Can some guru please tell me how and where to fix this, or can I do anything at all? Any help would be appreciated.

Indicated airspeed is the default. The higher your altitude (less dense air), the lower it reads, relative to true air speed (how quickly your "truely" moving through the air).

You can change your ASI to read "true" in the "realism settings". Or just get a feel for converting it in your head.