Hmmm, what version of Windows are you running. The GradientFill API is supposed to be in Win98 and above. You also need DirectX 8.1.
Note that grw88level2 only works with archived Level II data, not the real time Level III data like StormLab. It won't be of use in the current outbreak.
I'm running Windows 98 and I have DirectX 9.0b