You are well within the spec for FS2002. Minimum requirements are as follows:
Windows 98/Me(64Mb RAM) / Windows 2000/XP(128Mb RAM). 300MHz processor, 750Mb hard drive space, 8Mb graphics card.
Refresh rate relates to the speed at which your monitor refreshes the picture and is measured in Hz. A Riva TNT2 will be fine.
Enjoy the sim.