Hello, Julie I! I am not doctor. Here's what I do know. For a man in his mid 30's to have testicular cancer, he probably has cancer somewhere else in his body too. I do not know if both testicles will have to be removed, but if only one is cancerous and the other is healthy, there will be little or no effect on him as long as the surgery is all that has to be done to "cure" him of the cancer. Men can father children and have a wonderful sex life with only testicle. If both testicles must be removed, he will not be able to father children (of course), but he may have a normal sex drive since he is a mature man. There should not be any noticeable change in his appearances (body hair, musculature, etc) either. If there is the a strong likelihood that he will have to have both testicles removed, ask the doctors if he has healthy sperm cells that could be extracted for use later so that you two could have children in spite of the cancer.
Best to the two of you. You are going through challenging times. Hang in there!