Smilebasic isn't out in my region yet, but I did this exact thing in petit computer, and it was tougher than I expected. Split your problem into 3:
1: moving the sprite. detect the button presses and just slide it around the screen
2: getting it to face the right way. quite simple.
3: getting it to 'walk' animate while moving, and 'stand' while not moving. could be tricky.
I see you're trying to animate your sprite manually using spset. Not a terrible idea in general, but it would probably be better for you to learn how to use the proper sprite animation command SPANIM. It'll work out easier and more efficient in the long run...