I had my first job interview for a job at a Boy Scout camp a couple of months ago. I went in there not even knowing I was going to be interviewing. I was there for a bit more information about the job and I ended up interviewing on the spot with no preparation. My stutter was pretty bad the whole time, but I still got the job. I think the main thing is going to be how it will affect your job performance. Seeing as how you did very well for the majority of the interview, I think you'll do fine.