Ignore the kit instructions with regard to secondary. Secondary is more work and more opportunity to do something wrong with little to no benefit. Leave the beer in primary for at least 10 days and longer is probably going to be better. The additional time lets the yeast clean up and settle out out for a cleaner beer.
Oh, and the only time you can read your OG is before fermentation. Once the yeast start tearing into the sugar and converting to alcohol the gravity starts dropping. But like the others said, it's impossible to miss your target with extract unless your volume is off so don't worry about it.