No questions are silly if somebody wants to know the answer.  Like other cancers this is not contagious.    I think some people ask this because some viruses that may raise the likelihood of someone developing cancer (like Human Pappiloma Virus) are transmittable during sex but the cancer itself cannot be passed from person to person.  The nurses here may wish to confirm?

Although I am aware of Waldenstrom's Macroglobulinemia I know very little about it so I though it might help to direct you to the WMUK website (Waldenstrom's Macroglobulinemia UK); this has some useful information.  ALso the section headed "About WM" is interesting and has stories from other WM patients. 

Generally I would say treat your uncle as the man he always was before he became ill.  I don't know your family make-up and whether your uncle is for instance married or has children so don't know how much time you spend with him.  Take his lead on how much he wants to talk about his illness and don't wait to be asked to take on small tasks for the family that might be helpful.  I only say that because people often say "Tell me if I can help" but it doesn't happen so just jump in if you can do something useful.

I hope others might be able to give more useful information but I hope this will start you off.  Annie