I cyled mine with live rock. The smell in the house was kinda bad for a bit, but it worked fine for me. Someone will come along shortly and tell you about the related water changes while cycling this way. Can't do too much but gotta do some, I think. I don't remember to well (ya see, I got CRS ["S" means "stuff", of course] sometime
), but I don't think I changed mine until after the spikes.
As far as unwanted critters, some may be wanted. Diversity is a cool thing. Maybe you'll have time maybe to find'm and deal with them without any fish yet. Some say that's the fun of live rock. Mine didn't come with a lot of critters, so maybe someone else can help you there, but maybe a couple of things I've heard of are bad, like certain worms or the dreaded mantis.