Just be very careful when you do the bolts back up again when the new sprocket is on - they are like chocolate....I know this from experience/ineptitude.
"Ooooh, I'll just nip it up a little bit mo......ah, f**k!......lol....
If there is it might need to soak in overnight mate, followed by what moto suggested - a bit of tapping to "crack" the crap that's built up in the area.