I don't eat spam, but there isn't much you can do to it. I would be more concerned about the contents leaking all over my equipment. Spam is already cooked (and thoroughly preserved) so you just need to get it to the temperature you want to eat it at. I guess if I had left it out a couple days and it smelled ok, then I would boil it extra long just in case.
If you are concerned you could use pre-cooked bacon instead: