In which screen mode?
In tile-based screen mode (screen 0, 1, 2 et 4), you just have to write your new patterns in the Name table with any VRAM write function.
I don't know if there any function/sample to do that automatically, but it's quit simple to do.
If you need more information, feel free to ask here.
Well, I still have to study v9938 but I think that space mambow horizontal scrolling works in this way:
Set adjust (basic name, I still don't know how to name it in asm) positioning is used to move the screen 7 times, one pixel each frame. Then, at 8th frame the start position is restored and the whole nametable is shifted one column to the left and a new column is plotted to the rightmost position. To preserve scoreboard (upper rows) you have to synch with the related hblank (rasterline)