1. I think aliens exists, and we meet them very soon, so be ready ;)
And about the benefits we will see them when we meet them.
2. Yes. Everything.
3. Becouse its a good idea.
SETI@home and Astropulse are funded by grants from the National Science Foundation, NASA, and donations from SETI@home volunteers. AstroPulse is funded in part by the NSF through grant AST-0307956.