First of all, being new here myself, I find myself wading through literally dozens of topics everytime I come here. I don't search out specific topics or threads unless they were posted by myself to see what responses may have been made to my questions.
Just be patient. The answers will come and the people here WILL help you with your questions. Everyone here has been absolutely fantastic with me over the past few days and I'm sure you'll be treated just as well as I have.
Now, onto your question about mice and your snake. I would forget the mice and move up to rats. As has been posted both here and lesewhere, rats are far more nutritious for your pet than mice are. If he was being fed mice, that could be a major reason why is so underweight. I would get a couple of frozen rats and start there. Of course you only feed one frozen rat at a time and make sure it is thawed and warmed appropriately. I bet you'll find your new friend goes right after the little meal without much coaxing. Just be patient and take your time with your new pet. Give it the care and love it requires and you'll have a friend for life, guarenteed.
BTW, post some pics of your new addition to the family! I know we'd all love to see it!