The most important thing before speaking at a funeral is staying calm. It is not like you are at a job or in school. Take your time. You are paying respect to your loved one and they deserve all the time they want. If you have to read word for word what you wrote, do that. It is the words that are important. You are honoring the deceased not the people who are there.
Make sure that you speak clearly and slowly. If you are going to talk, do make sure that everyone understands and hears what you are saying. Again, take all the time that you want just make sure that your speech is delivered in a reasonable manner.
As far as what you want to write and convey, that is up to you. If you are talented enough to not look at your paper and use certain keywords, go ahead and do that. Still, the main thing is honoring your loved one and they deserve the limelight. Do not rush and if you have to read word for word from what you wrote, go ahead and go that route. Most importantly, speak clearly and loud enough so that everyone can hear you.