1. The fact that scientists refer to the 'theory of evolution' rather than the 'evolutionary hypothesis' means that evolution is strongly backed by observations, both in nature and in the lab, and has strong explanatory and predictive power in its area. If you want 100% answers, become a mathematician; otherwise, science is perfectly happy with 99.999...% certain. A scientific theory is NOT a guess. When scientists refer to a theory, they refer to something that is backed by observation and experiment, explains a class of observations, and can predict the outcome of future observations.
If you want 100% certainty in biology, then I want to see you protesting "Daltonist priests of atomism" and demanding that the alternate theory of 'earth, fire, air, and water' be taught in chemistry. I want to see you getting rid of your cell phone because relativity is "just a theory" therefore the GPS unit in it isn't "proven".
Because if you doubt evolution because of a mythical 100% certainty standard, then not having the same reservations towards chemistry and physics is pure hypocrisy.
2. I second Aron Ra's series on The Systematic Classification of Life, already pointed to by Robin W.
3. Creationists aren't biologists, and a theological objection to a scientific theory is irrelevant. They can write whatever books they like; they will continue to have no bearing on or refutatory value against evolutionary theory. If you want to refute evolution, you're going to need to do it in the field and in the lab and in peer-reviewed papers, not in the pulpit.
4. Most mainstream religions have no problem with evolution. I was taught evolution in my Catholic high school. You may have trouble reconciling the two if you have a fundamentalist religious view, but that's not a problem for evolution, that's a personal issue.