A littl curious about Red Dead Redemption?

I just purchased this game online, and I was a fan of previous games such as red dead revolver and gun, and also fallout 3 due to their large map and roaming capabilities. And i had read a couple reviews on RDR but I had a couple questions for u guys. How big exactly is the area you can roam aroud in and the map? Can you save at various points so you can screw around and lets say shoot up a town and load and youll be fine? Also is there lots of side missions, those are some of my favorite things about games like those. Also do you think overall i will enjoy this game? Thank you for your feedback.