No problem! Some other, more experienced people that can probably help you more are @NatJ , @rosemarythyme , @3KillerBs , and @aart . Good luck with your flock!
It is best to integrate more than one at a time. That way they're not completely isolated from the rest and will integrate much more easily. Any age should work if the integration is done properly. Polishes and Sultans can be tough to integrate because of their poor sight. I would pick something...