I have an e-book ready and good to go - is there anything I need to know before I try selling it?

Is it acceptable to sell an e-book via paypal? If not, what other service should I use to accept payment?

Are there any legal concerns to be aware of? Am I allowed to just put up a site and accept payment for an e-book?

Has anyone successfully written and sold an e-book? Any advice?

Thanks for any insight!