That is the same setup I have and I get decent results with it.
Some tips: get a tripod(a good one if you can swing it, eg Bogen or better), turn your pumps off for coral shots, shoot straight through the glass to avoid distortions, use the histogram function to check exposure, use the self timer function.
Post pics once you are up and running.
As a warning though, you will want a macro lens eventually. If you can get the kit with the 18-55 and a good macro, do it!