You're a bit light on information. The keel can most likely be filled in with epoxy/glass. Not very expensive. I'm assuming it's lead since it dented. The rudder is another story. Depends on the damage extent. A small chunk may need the same fill in. Damage to the structure of the rudder may need replacement. Minor bending or the rudder shaft can be straightened at a machine shop but obviousIy you have to take the rudder off. At worst you may have to dig a hole to do that. I can tell you from experience that fin keel sailboats don't drive too good without a rudder. Foss foam will make you a new one, but cheap is not a word I would use for that solution. The caulking falling out I don't understand. Fell out from where?
We really need some pictures.