advice on heartworms in an older dog

I need some advice on what to do. We have a pug that was given to us just before Thanksgiving last year by a family member. He had been rather neglected by them. After we had him for a few weeks he developed a respiratory infection and we took him to the vet. He was put on antibiotics and that cleared up, but seems to be recurring. The vet said he is between 8-10 years old. He also diagnosed him with heartworms and wants to do the treatment on him. I've read up on the treatment and it seems that it is very hard on the animal and he may not survive. I'm worried that the vet is out to just make money and not really concerned with the dog's actual health. We have grown very attached to Percy and could not ask for a better dog. The problem is not the cost of the treatment, but whether or not he will survive it. Has anybody else had this treatment done before and if so how did your dog handle it? Should we check around for a second opinion or go ahead and risk the treatment?