Using same theme and navagtion on network

I have been hard at work figuring out using multisite and learning wordpress. I must say I really love this program. My block I’ve run into though is when creating a network and having multiple blogs on the same site is that I would like each blog to have the same menu and navigation along with the same theme. Maybe some different images used but still all the same style. Is there some kind of plugin that will do this or am I missing a check box setting somewhere? Sorry if this is a silly question but I would really like to know since it will make the type of sites I’m interested creating the future much easier.

Thank you for any help you can give and also thanks for all the help you have already given from all the posts I have researched here coming into this.