1. Different types of GPU memory, common modern computers is DDR5 for GPU cards.. no cards are made with 3 or 4 for years now
2. Most are in Ghz which is 1000Mhz. Not sure why you need this and is normally listed with your GPU specfications, but no one pays attention to this.
The Flight Simulator program, how old is it? It sounds like the old MS Flight Simulator from back in Windows 98 days? If so then it may not work at all with modern equipment. If you try to run the program in compatibility mode (right click shortcut, select compatibility) you can set it to the version of OS most likely it was made for but if your on Windows 7/8 I wouldnt' try anything less compatible them XP, it isn't worth it and not really going to perform as expected.