I'm in a similar boat as you. I really would love to help rehab large mammals in the Northern parts of the U.S. I've looked into Wildlife and Forestry Conservation through Penn Fosters web site where you can take online course for a fair price ($600). But I get mixed emotions about it. Some say it's not worth it, some say it is. I've found forums where people say to get into contact though your states wildlife fish and game services and talk to their adviser about programs and what type of information I would need to per sure a career in that type of field. Good luck. =]