Start here:
School Bus Conversion Resources - Search Results
Read this with special attention to the "Help choosing a bus" thread.
You will come up with lots of questions. Then you can ask specific questions and folks here are great about sharing their knowledge and experience.
Keep in mind that this is work with a LOT of decisions to make along the way. The ability to search not only this site but the whole world of the Web is a very valuable skill in that process. It may be invaluable to you to sharpen your research skills so that you can better tap this resource.