Well, as for hurting you, I really don't know, you might have to do some more research online before trying.
What do you mean, is what okay even if you are spotting?
When I researched IUDs, I never heard anyone complain about CONSISTENT infections. It really shouldn't happen if both of you are sanitary...!
Really, don't worry about it, this really is not a big deal. I think it's very unlikely that YOUR body is going to be so much more prone to infection than countless other people's.