Don't worry, public speaking nerves won't... kill you.
"It won't kill you." Picture by Bart Groenhuizen.
I was giving a talk and the person who had gone before me (my boss, of course) had offended this group of people. To say they were hostile towards what I had to say was heavily understating the case.
I did my talk with my overheads, realized that it wasn't my fault they were hostile, figured out that their hostility was really unwarranted, and got myself out of there.
What I learned is that I was able to survive the worst case scenario for any speaker. I have been in that situation a time or two since then. I just get some spit back in my mouth, take a deep breath, and realize that they won't kill me. I'll survive.