Screensaver for a client

hi, a client just asked me to make them an animated screensaver for their computers in the office, Im thinking in doing it in flash of course, perhaps with some AE…but I have some questions because Ive never do this before.

1-After I make the animation, which is a good program to convert the swf into a screensaver? better if its free :snug:

2-how big should the file be? (I know it depends in the computer speed but tell me a good number)

3-how much should I charge? Probably its going to be one day of work

4-Anything I should know about this?