Change Database from ISO8859-1 to UTF8 and import pmachine archives to wordpress

I have a 10 year old weblog - www.webmercial.dk. It is hosted on wordpress, and character encoding is ISO8859-1. I need to change that to UTF8, without changing ?,? and ? in the archives to unreadable signs. Secondly: I have a pmachine-archive of the weblog in a sql dump. At some time I started entering archives manually, but never finished the task. I need to insert missing posts. Thirdly: at some time all comments were truncated whenever a "?,? or ?" was encountered. I have a sql-dump with those comments - they need to be restored.