Surgery For Gooby

This is my little baby guy,Gooby.he is five years old,and he is my life.He was attacked by another dog,he has to have his leg removed because of his injuries,for 500$ they can remove his leg,or for 3000 they can try to save it.but the vet won't do either until I have the money upfront.so until then all we can do is make him comfortable.he is in alot of pain,he has medication for that.still very hard to watch him suffer.they put a temporary splint on him.thats all they can do until we pay to have it removed.even though I would love to save his little leg,I know getting it amputated is the going to be what is going to be done.500 is more reasonable then the 3000 is to save his leg.it has to be done very soon.i need help .the vet won't touch him without that money .he is my best friend,and I failed to keep him safe,please help me help him.i don't want him in pain any longer then he has to be. Thank you for any support You can give.