Bill,
I have replaced the slide seals on several coaches, and it is no an easy job, but with care and patience the average DIY mechanic should be able to do it. However, you will probably find that you need to replace the outer seals all of the way around the slide, because the leak is probably on the side or top of the slide and it is running down between the inner and outer seals until it pools at the bottom where it finds a way into the coach.
Gerald