Bought a coop..well almost! Disinfecting?

I put a deposit down on a coop. Have to go pick it up with the horse trailer and pay the ballance. The coop its self is about 4x4, the attached run is almost 10'. It is in good shape, might make some minor improvements. It is technically a chicken tractor, but the hinge for the wheels is a bit..loose, so not sure how long it will "tractor". I paid $150 for it and it is under 2 years old. Good deal??
Anyways, should I try to disinfect the coop? If so how?I will be getting some 4 week old chicks next week so they will not be inhabiting for a little while I guess. But do not want to use anything that would be harmful to the chickens.
I am so excited that I am getting closer to chicken ownership! Eventually we will be fixing up our old 6'x14' coop, but this will do for now. I was told the previous owners had 5 RIR in this coop comfortably. I think I will be getting 3-4, is this ok? They will be able to free range quite a bit.