Hmm, if the chain is being pushed off the teeth of the front sprocket it could be that your chain is not tight enough. These chains need to be pretty darn tight, I read somewhere that the chain should only move up and down 1/4 inch.
I'm not sure how to get the front sprocket off, I'm sure there are lots of people on this forum that can help you; its full of helpful people that know the bike kits inside and out.