The guy who writes "No Lawyers, Only Guns and Money" posted this transcript of a letter on his blog. He says feel free to copy and paste it.
http://onlygunsandmoney.blogspot.com...o-send-to.html
I wouldn't worry to much about great fact and statistics. All of these emails are read by an intern, who at the end of the day tallies up the pro- and anti- messages and delivers a report to the Congressional rep or his/her chief of staff.
The important thing is to write! And write like they vote in Chicago, early and often.