Clown and other preliminary fish questions??

Hi, we are still cycling our 75 gallon but it should be done or close to done. Starting next week if the water tests out ok we are going to look at getting a pair of the common percula clowns to start with. Anyone have good suggestions on how to remove the 5 damsels first? We have a large amount of live rock and decorations in the tank and it seems like it will be impossible unless we pull everything out and I don't know that is advisable. We have a number of hitchhikers we have picked up in our live rock like star fish, snails and a Hawaiian Feater Duster. Also, someone on reef central I think told me I need a pair of same species juvenile clowns. We want the common orange perculas but does size make a difference? Also, I would like to add a third fish about the same time, is there any danger with doing that? Thanks so much for wisdom as we are trying to learn but have no experience to this point!
John