Question: "Now we just need the 50 bucks. Damn it, I knew I shouldn't have named that star for Mort. Ugh! Just give me the money." I didn't understand that joke - can someone please explain it to me?
Answer: There are companies in real life that will let you name stars after someone as a gift (although the star name won't go on any official government registry). You pay a company (in Peter's case for $50) for this privilege and they'll send that you information where the star is located. Mort is then looking at the star named after him. But it's as useless of a gift as you can imagine since it doesn't really mean anything and you can't do anything with it and Mort knows Peter spent money to do it. Mort would rather have had Peter just give him $50 cash as a gift. One could say it's a joke about the stereotype that Jews love money, but in this case a lot of people would rather have money over a useless gift.
Answer: Loons are aquatic birds that make a very unique sound. Early, when Peter and Louis are going up to the cabin, Peter stops and gets out of the car to listen to a loon. It's just showing how easily Peter gets distracted because he's suppose to be hurrying to prevent Quagmire and Meg having sex. "We heard a loon" is what Lois writes in the guest book, which indicates they had a pleasant trip up to the cabin when really they should still be mad at Quagmire. I haven't found any joke or movie reference to the line, but it fits Peter.