It is worth having someone there who knows what they are doing for the first time. But it is a very easy process. If your blade is not sealed, take the rubber off carefully and slowly. If you are putting new rubber on, put glue on both the wood and the rubber. Let the rubber dry. Then put the rubber on the wood. Press it, or if you have a tube or pipe, roll it.
There are two ways to cut it. 1) with a scissor; this is very easy. You just have a good sharp scissor and you cut right up to the edge of the blade and cut around.
2) With a heavy grade X-Acto knive. One of the ones with a handle like a screwdriver. With this you need a surface like a cutting board and a a blade for carving and trimming. You just cut around the blade with the knife. This one takes some time to get used to. I use this more for when I am trimming a rubber that has expanded or is too big for the blade I am putting it on, but has already been cut. A scissor does not work so well on cutting a tiny bit of the edge of a rubber whereas an X-Acto knife will do this job well.
Once the first side is cut. You glue the second sheet on in the same way and then you cut the second sheet. Really very easy but worth seeing someone doing it or doing it with someone there who knows how to do it.